Slide 1 — Aggregate Demand: Learning Objective and Basic Concepts （第1页——总需求：学习目标与基本概念）

Knowledge Points (知识点)

Aggregate demand (AD) curve and its definition（总需求曲线及其定义）
Short-run aggregate supply (SRAS) curve and its definition（短期总供给曲线及其定义）
AD–SRAS model and the macro learning objective（AD–SRAS 模型与本章学习目标）

🔹Knowledge Point 1 — Aggregate Demand (AD) Curve（总需求曲线）

Explanation（解释）
The aggregate demand curve shows the relationship between the overall price level and the quantity of real GDP demanded by households, firms, and the government (and net exports).
总需求曲线表示整体物价水平与家庭、企业、政府（以及净出口）所需求的实际 GDP 数量之间的关系。

A movement along the AD curve is caused only by a change in the overall price level.
沿着 AD 曲线的移动只由整体物价水平的变动引起。

Example（例子）
If the price level falls from 120 to 110, households, firms, and the government demand more goods and services, so real GDP demanded rises from, say, 16 to 17 trillion dollars.
如果物价水平从 120 降到 110，家庭、企业和政府会想购买更多商品和服务，需求的实际 GDP 量就可能从 16 万亿增加到 17 万亿美元。

Extension（拓展）
Aggregate demand can be decomposed as
$A D = C + I + G + NX$
where $C$ is consumption, $I$ is investment, $G$ is government purchases, and $NX$ is net exports.
总需求可以分解为
$A D = C + I + G + NX$ ，
其中 $C$ 为消费， $I$ 为投资， $G$ 为政府购买， $NX$ 为净出口。

🔹Knowledge Point 2 — Short-run Aggregate Supply (SRAS) Curve（短期总供给曲线）

Explanation（解释）
The short-run aggregate supply curve shows the relationship in the short run between the price level and the quantity of real GDP supplied by firms.
短期总供给曲线表示在短期内，物价水平与企业愿意提供的实际 GDP 数量之间的关系。

In the short run, wages and some input prices are sticky, so changes in the price level affect firms’ profits and hence output.
在短期内，工资和部分投入价格具有粘性，因此物价水平的变动会影响企业利润，从而影响产出。

Example（例子）
If output prices increase while wages are fixed for a year-long contract, firms’ profits rise and they expand production, so quantity of real GDP supplied increases.
如果产品价格上升而工资在一年合约内保持不变，企业利润上升，会扩大生产，从而使提供的实际 GDP 数量增加。

Extension（拓展）
SRAS is upward sloping because when the overall price level rises while many costs are fixed in the short run, the real wage falls and firms find it profitable to hire more workers and produce more.
SRAS 向上倾斜，是因为在许多成本短期固定时，整体物价水平上升会降低实际工资，使企业增加雇佣和产出更有利可图。

🔹Knowledge Point 3 — AD–SRAS Model and Learning Objective（AD–SRAS 模型与学习目标）

Explanation（解释）
The intersection of the AD and SRAS curves determines the short-run equilibrium price level and real GDP for the economy as a whole.
AD 与 SRAS 曲线的交点决定了整个经济在短期内的均衡物价水平和均衡实际 GDP。

The learning objective is to identify the determinants of aggregate demand and to distinguish between movements along the AD curve and shifts of the curve.
本章学习目标是：识别总需求的决定因素，并区分“沿 AD 曲线的移动”和“AD 曲线的整体移动（平移）”。

Example（例子）
If consumer confidence rises, households spend more at each price level, shifting the AD curve to the right instead of moving along the same AD curve.
如果消费者信心提高，家庭在任何给定物价水平下都愿意多花钱，AD 曲线会整体右移，而不是在原曲线上移动。

Extension（拓展）
Later analysis adds long-run aggregate supply (LRAS) to show how short-run fluctuations relate to potential GDP and long-run growth.
在进一步分析中，还会加入长期总供给曲线（LRAS），用来说明短期波动与潜在 GDP 以及长期增长之间的关系。

本页小结（Summary）
The AD curve links the price level to total spending, the SRAS curve links the price level to firms’ production in the short run, and their intersection gives the economy’s short-run equilibrium.
AD 曲线把物价水平与总支出联系起来，SRAS 曲线把物价水平与企业短期产出联系起来，它们的交点给出经济的短期均衡。

Slide 2 — Aggregate Demand and Short-run Aggregate Supply Diagram （第2页——总需求与短期总供给图示）

Knowledge Points (知识点)

Graphical representation of AD and SRAS（AD 与 SRAS 的图形表示）
Short-run macroeconomic equilibrium（短期宏观均衡）
Interpretation of the equilibrium point（均衡点的含义）

🔹Knowledge Point 1 — AD and SRAS in a Diagram（图中的 AD 与 SRAS）

Explanation（解释）
The vertical axis measures the price level (e.g., GDP deflator, $2009 = 100$ ) and the horizontal axis measures real GDP in trillions of dollars.
纵轴表示物价水平（例如，以 2009 年为 100 的 GDP 平减指数），横轴表示以万亿美元计的实际 GDP。

The downward sloping curve is aggregate demand, AD; the upward sloping curve is short-run aggregate supply, SRAS.
向下倾斜的曲线是总需求 AD；向上倾斜的曲线是短期总供给 SRAS。

Example（例子）
On the graph, the economy is shown at an equilibrium where the price level is 110 and real GDP is $17.0 trillion.
在图中，经济处于物价水平为 110、实际 GDP 为 17.0 万亿美元的均衡点。

Extension（拓展）
Shifts in AD or SRAS will move the intersection point, changing both the equilibrium price level and real GDP.
AD 或 SRAS 的任何平移都会改变交点，从而改变均衡物价水平和均衡实际 GDP。

Image/Data Analysis（图像或数据分析）
The equilibrium point is where AD and SRAS intersect; the dashed lines from this point to the axes show the corresponding equilibrium price level (110) and real GDP ($17.0 trillion).
交点处画出的虚线分别连接到纵轴和横轴，标出均衡物价水平 110 和均衡实际 GDP 17.0 万亿美元。

🔹Knowledge Point 2 — Short-run Macroeconomic Equilibrium（短期宏观均衡）

Explanation（解释）
Short-run equilibrium occurs where quantity of real GDP demanded equals quantity of real GDP supplied at the prevailing price level.
短期均衡发生在在给定物价水平下，需求的实际 GDP 数量等于供给的实际 GDP 数量的点上。

Example（例子）
If firms plan to supply $17.0 trillion of output at price level 110, and households, firms, government, and foreign buyers together plan to purchase exactly $17.0 trillion at that price level, the economy is in short-run equilibrium.
如果在物价水平 110 时，企业计划供给 17.0 万亿产出，而总需求各部分恰好也计划购买 17.0 万亿，那么经济就在短期均衡上。

Extension（拓展）
When actual real GDP is above or below potential GDP, policymakers may use fiscal or monetary policy to shift AD and reduce economic fluctuations.
当实际 GDP 高于或低于潜在 GDP 时，政策制定者可以通过财政或货币政策推动 AD 平移，以减缓经济波动。

Image/Data Analysis（图像或数据分析）
If AD shifts right while SRAS stays fixed, the intersection moves up along SRAS, giving a higher price level and higher real GDP. If SRAS shifts left (e.g., cost shock), the intersection moves up along AD, giving a higher price level but lower real GDP.
若 AD 右移且 SRAS 不变，交点沿 SRAS 向上移动，物价和实际 GDP 都上升；若 SRAS 左移（如成本冲击），交点沿 AD 向上移动，物价上升但实际 GDP 下降。

🔹Knowledge Point 3 — Why We Need Macroeconomic Explanations（为何需要宏观层面的解释）

Explanation（解释）
Because we analyze the economy as a whole, we use macroeconomic reasoning to explain why the AD curve slopes downward, why SRAS slopes upward, and why these curves shift over time.
由于分析对象是整个经济，我们需要运用宏观经济学的逻辑来解释：为什么 AD 曲线向下倾斜、SRAS 曲线向上倾斜以及两条曲线为何会发生平移。

Example（例子）
Micro demand for a single good can fall when its own price rises; at the macro level, we instead focus on how the overall price level affects total spending and production.
微观中某种商品价格上涨会使该商品需求下降；而在宏观中，我们关心的是整体物价水平的变化如何影响总支出和总产出。

Extension（拓展）
The wealth effect, interest-rate effect, and international-trade effect together explain the downward slope of the AD curve; later chapters add more detail on each channel.
财富效应、利率效应和国际贸易效应共同解释 AD 曲线向下倾斜；后续章节会分别展开讨论这些渠道。

本页小结（Summary）
The AD–SRAS diagram shows short-run macro equilibrium at the intersection of downward-sloping AD and upward-sloping SRAS, and macroeconomic mechanisms explain the slopes and shifts of these curves.
AD–SRAS 图通过向下倾斜的 AD 和向上倾斜的 SRAS 的交点展示短期宏观均衡，而宏观经济机制则解释这些曲线的斜率与移动。

Slide 3 — Why Is the Aggregate Demand Curve Downward Sloping? The Wealth Effect （第3页——为什么总需求曲线向下倾斜？财富效应）

Knowledge Points (知识点)

Definition of the wealth effect on consumption（财富效应的定义）
How price level changes affect real wealth and consumption（物价水平变化如何影响实际财富与消费）
Why the wealth effect makes the AD curve downward sloping（财富效应为何使 AD 曲线向下）

🔹Knowledge Point 1 — Wealth Effect and Household Consumption（财富效应与家庭消费）

Explanation（解释）
The wealth effect is the impact of changes in the price level on the real value of household wealth and therefore on consumption.
财富效应指物价水平变化通过改变家庭财富的实际价值，进而影响消费的过程。

Current income is the main determinant of consumption, but consumption also depends on household wealth, defined as the value of assets minus the value of debts.
当前收入是决定消费的最重要因素之一，但消费同样取决于家庭财富，即资产价值减去负债价值。

Example（例子）
If a household holds $10,000 in cash or bank deposits, and the price level rises by 10%, the real purchasing power of that nominal wealth falls by about 10%.
如果一个家庭持有 10,000 美元现金或存款，当物价水平上升 10% 时，这些名义财富的实际购买力大约下降 10%。

Extension（拓展）
In simple terms, real wealth can be written as
$W^{re a l} = \frac{W ^{n o mina l}}{P}$ ,
so when the price level $P$ rises and nominal wealth is unchanged, $W^{re a l}$ falls.
简单表示为：实际财富 $W^{re a l} = \frac{W ^{n o mina l}}{P}$ ，因此在名义财富不变时，物价水平 $P$ 上升会压缩实际财富。

🔹Knowledge Point 2 — Price Level, Real Wealth, and Consumption（物价水平、实际财富与消费）

Explanation（解释）
Some household wealth is held in cash or other nominal assets whose nominal value is fixed in the short run, so changes in the price level change their real value.
部分家庭财富以现金或其他名义资产形式持有，其名义金额短期固定，因此物价水平变化会改变其实际价值。

When the price level rises, the real value of household wealth falls, reducing consumption and the demand for goods and services.
当物价水平上升时，家庭财富的实际价值下降，消费支出减少，对商品和服务的需求下降。

When the price level falls, the real value of wealth rises, and households increase consumption, raising demand for goods and services.
当物价水平下降时，家庭财富的实际价值上升，家庭会增加消费，对商品和服务的需求上升。

Example（例子）
If a family’s bank balance remains $20,000 but the price level falls by 5%, the real purchasing power of that balance rises by about 5%, encouraging extra spending on durable goods or vacations.
如果一个家庭的银行存款仍为 20,000 美元，而物价水平下降 5%，则这笔存款的实际购买力提高约 5%，家庭可能会增加对耐用品或度假的支出。

Extension（拓展）
Similar logic applies to bonds or fixed-income assets whose nominal payments are preset; unexpected inflation erodes their real value, while unexpected deflation raises it.
同样的逻辑适用于名义收益固定的债券和其他固定收益资产：意外的通货膨胀会侵蚀其实际价值，而意外的通货紧缩会抬高其实际价值。

🔹Knowledge Point 3 — Wealth Effect and the Downward Slope of the AD Curve（财富效应与 AD 曲线向下倾斜）

Explanation（解释）
Because a higher price level reduces real wealth and consumption, and a lower price level increases them, total quantity of real GDP demanded moves inversely with the price level.
由于较高的物价水平会削弱实际财富和消费，而较低的物价水平会提升它们，因此需求的实际 GDP 数量与物价水平成反向变动关系。

This inverse relationship is one key reason why the aggregate demand curve slopes downward.
这种反向关系是总需求曲线向下倾斜的一个重要原因。

Example（例子）
Moving from a higher price level $P_{1}$ to a lower price level $P_{2}$ along the AD curve increases real wealth and consumption, so the economy moves from a point with lower real GDP demanded $Y_{1}$ to a point with higher real GDP demanded $Y_{2}$ .
沿着 AD 曲线从较高物价水平 $P_{1}$ 移到较低物价水平 $P_{2}$ 时，实际财富和消费都会增加，经济从需求较低的产出水平 $Y_{1}$ 移到需求较高的 $Y_{2}$ 。

Extension（拓展）
In a full macro model, the wealth effect works alongside the interest-rate effect (price level and real money balances) and the international-trade effect (price level and net exports), all reinforcing the downward slope of the AD curve.
在完整的宏观模型中，财富效应与利率效应（物价水平与实际货币余额）以及国际贸易效应（物价水平与净出口）共同作用，加强了 AD 曲线向下倾斜的特征。

本页小结（Summary）
Changes in the overall price level alter the real value of household wealth; this wealth effect changes consumption and helps explain why the aggregate demand curve slopes downward.
整体物价水平的变化会改变家庭财富的实际价值，经由财富效应影响消费，从而帮助解释总需求曲线为何向下倾斜。

Slide 4 — The Interest-Rate Effect on Investment （第4页——利率效应与投资）

Knowledge Points (知识点)

Definition of the interest-rate effect（利率效应的定义）
How higher price levels raise interest rates and reduce investment（物价上升如何推高利率并减少投资）
How lower price levels reduce interest rates and increase aggregate demand（物价下降如何降低利率并提高总需求）

🔹Knowledge Point 1 — Interest-Rate Effect（利率效应）

Explanation（解释） The interest-rate effect describes how a change in the price level alters money demand, interest rates, and ultimately investment and consumption. 利率效应指物价水平变化如何影响货币需求与利率，进而改变投资和消费。

When the price level rises, households and firms need more money for transactions, so they withdraw deposits, borrow, or sell financial assets, increasing money demand and pushing interest rates up. 当物价水平上升时，家庭和企业为了完成交易需要更多货币，于是提取存款、借款或抛售金融资产，从而提高货币需求并推高利率。

Example（例子） If prices rise by 5%, firms must hold more cash to pay for wages and materials; they may borrow more from banks, which increases the demand for loanable funds and raises the market interest rate. 如果物价上涨 5%，企业需要更多现金支付工资和原材料，可能会向银行多借款，从而增加可贷资金需求并推高市场利率。

Extension（拓展） In money market models, a higher price level shifts the money demand curve to the right, raising the equilibrium nominal interest rate and reducing interest-sensitive spending. 在货币市场模型中，较高的物价水平会使货币需求曲线右移，提高均衡名义利率，从而减少对利率敏感的支出。

🔹Knowledge Point 2 — Higher Interest Rates and Lower Investment（高利率与较低的投资）

Explanation（解释） Higher interest rates make borrowing more expensive for firms and households. Firms cut back on investment in factories, machinery, and equipment; households borrow less for houses and other big-ticket items. 较高的利率会提高企业和家庭的借款成本，企业会减少在工厂、机器和设备上的投资，家庭也会减少购房等大额借款。

As investment spending falls, the quantity of goods and services demanded decreases, reducing real GDP demanded. 随着投资支出下降，对商品和服务的总需求减少，需求的实际 GDP 水平也随之下降。

Example（例子） If the interest rate rises from 4% to 7%, a firm may cancel a planned factory expansion because the present value of expected profits is no longer high enough to cover the higher financing cost. 如果利率从 4% 升至 7%，某企业可能会取消扩建工厂的计划，因为预期利润的现值不足以覆盖更高的融资成本。

Extension（拓展） Consumption spending on durable goods such as cars and appliances is also interest-sensitive; higher interest rates reduce borrowing for these items and further weaken aggregate demand. 耐用品消费（如汽车、电器）同样对利率十分敏感；较高利率会减少相应借款，进一步削弱总需求。

🔹Knowledge Point 3 — Lower Interest Rates and Higher Aggregate Demand（低利率与更高的总需求）

Explanation（解释） Conversely, when the price level falls, money demand declines, interest rates drop, and investment and some consumption spending increase, raising aggregate demand. 相反，当物价水平下降时，货币需求减少，利率下降，投资以及部分消费支出上升，从而提高总需求。

The interest-rate effect is a second key reason why the aggregate demand curve slopes downward. 利率效应是解释总需求曲线向下倾斜的第二个重要原因。

Example（例子） A fall in the price level reduces the transactions demand for money; with less competition for funds, interest rates fall, encouraging firms to start new projects and households to finance new homes. 物价水平下降会降低交易性货币需求；资金竞争减弱，利率下降，企业更愿意启动新项目，家庭也更愿意贷款购房。

Extension（拓展） In the AD–SRAS diagram, a fall in the price level moves the economy down along the AD curve to a point with lower interest rates and higher levels of investment and output demanded. 在 AD–SRAS 图中，物价水平的下降使经济沿 AD 曲线向下移动到利率较低、投资和需求产出更高的新点上。

本页小结（Summary） A higher price level raises money demand and interest rates, reducing investment and some consumption; a lower price level does the opposite. This interest-rate effect helps explain the downward slope of the AD curve. 较高物价水平会提高货币需求和利率、压低投资与部分消费，而较低物价水平则相反；利率效应因此成为总需求曲线向下倾斜的重要原因之一。

Slide 5 — The International-Trade Effect on Net Exports （第5页——国际贸易效应与净出口）

Knowledge Points (知识点)

Definition of net exports and the international-trade effect（净出口与国际贸易效应的定义）
Higher domestic price levels and lower net exports（本国物价上升与净出口下降）
Lower domestic price levels and higher net exports（本国物价下降与净出口上升）

🔹Knowledge Point 1 — Net Exports and International-Trade Effect（净出口与国际贸易效应）

Explanation（解释） Net exports are defined as exports minus imports: $NX = X - M$ . 净出口等于出口减去进口： $NX = X - M$ 。

The international-trade effect describes how a change in the domestic price level relative to foreign price levels affects exports, imports, and hence net exports and aggregate demand. 国际贸易效应指本国物价水平相对于外国物价水平的变化如何影响出口、进口，从而影响净出口与总需求。

Example（例子） If U.S. prices rise relative to European prices, U.S. goods become more expensive to both Americans and Europeans, while European goods become relatively cheaper. 如果美国物价相对于欧洲物价上升，美国商品对美国人和欧洲人来说都更贵，而欧洲商品相对更便宜。

Extension（拓展） Because net exports are one component of aggregate demand ( $A D = C + I + G + NX$ ), any change in $NX$ directly shifts the level of aggregate demand at each price level. 由于净出口是总需求的组成部分之一（ $A D = C + I + G + NX$ ）， $NX$ 的变化会直接改变各个物价水平下的总需求。

🔹Knowledge Point 2 — Higher Domestic Prices and Lower Net Exports（本国物价上升与净出口下降）

Explanation（解释） When the domestic price level rises relative to other countries, domestic products become relatively more expensive and foreign products relatively cheaper. 当本国物价水平相对于其他国家上升时，本国产品相对变贵，外国商品相对变便宜。

Some foreign buyers switch from buying this country’s goods to buying goods from other countries, and some domestic consumers switch from domestic goods to imports. Exports fall and imports rise, causing net exports to decline. 部分外国买家会从购买本国产品转向购买他国产品，一些本国消费者也会从国产品转向进口品；出口减少、进口增加，净出口下降。

As net exports fall, the quantity of domestic goods and services demanded falls, lowering aggregate demand. 净出口下降意味着对本国产品和服务的总需求下降，从而降低总需求。

Example（例子） If U.S. price levels rise while Japanese prices remain stable, U.S. cars become more expensive than Japanese cars, so both Americans and foreigners may buy more Japanese cars and fewer U.S. cars. 如果美国物价上升而日本物价保持稳定，美国汽车比日本汽车更贵，美国人和外国人都可能更多购买日本车、减少购买美国产车。

Extension（拓展） A sustained loss of international price competitiveness can lead to trade deficits and slower GDP growth in open economies. 在开放经济中，如果长期丧失国际价格竞争力，可能导致贸易逆差并拖累 GDP 增长。

🔹Knowledge Point 3 — Lower Domestic Prices and Higher Net Exports（本国物价下降与净出口上升）

Explanation（解释） When the domestic price level falls relative to other countries, domestic goods become relatively cheaper and foreign goods relatively more expensive. 当本国物价水平相对他国下降时，本国产品变得更便宜，外国商品则相对更贵。

Exports rise and imports fall, so net exports increase, raising the quantity of domestic goods and services demanded. 此时出口增加、进口减少，净出口上升，对本国产品和服务的需求量提高。

The international-trade effect is a third reason why the aggregate demand curve slopes downward. 国际贸易效应是解释总需求曲线向下倾斜的第三个原因。

Example（例子） If prices in the United States fall while prices in other countries stay the same, foreign consumers find U.S. software, farm goods, and manufactured products cheaper and increase their purchases, while U.S. consumers buy fewer imports. 如果美国物价下降而其他国家物价不变，外国消费者会发现美国的软件、农产品和制造品更便宜并增加购买，美国消费者也会减少进口。

Extension（拓展） Exchange rate movements interact with relative price levels; a depreciation of the domestic currency can have similar effects to a fall in domestic prices by making exports cheaper and imports more expensive. 汇率变动也会与相对物价共同作用；本币贬值会像物价下降一样，使出口更便宜、进口更昂贵，从而改善净出口。

本页小结（Summary） When a country’s prices rise relative to others, its exports fall and imports rise, reducing net exports and aggregate demand; when its prices fall, net exports and aggregate demand increase. This international-trade effect further explains the downward slope of the AD curve. 当一国物价相对他国上升时，出口下降、进口上升，净出口和总需求减少；当物价下降时，净出口和总需求上升。国际贸易效应因此进一步解释了总需求曲线向下倾斜。

Slide 6 — Shifts of the AD Curve versus Movements along It （第6页——总需求曲线的移动与沿曲线移动）

Knowledge Points (知识点)

Movement along the AD curve: caused by price-level changes only（沿 AD 曲线移动：仅由物价变化引起）
Shifts of the AD curve: caused by non-price factors（AD 曲线的平移：由非价格因素引起）
Main categories of variables that shift AD（推动 AD 曲线平移的主要变量类别）

🔹Knowledge Point 1 — Movements along the AD Curve（沿 AD 曲线的移动）

Explanation（解释） The aggregate demand curve shows the relationship between the price level and quantity of real GDP demanded, holding all other variables constant. 总需求曲线在“其他条件不变”的假设下，描述物价水平与需求的实际 GDP 数量之间的关系。

If the price level changes but all other determinants of spending remain unchanged, the economy moves up or down along a stationary AD curve—this is a movement along the curve, not a shift. 当物价水平发生变化而其他影响支出的变量保持不变时，经济只是沿着既定的 AD 曲线上下移动，而不是整条曲线平移。

Example（例子） A fall in the price level from 110 to 105, holding income expectations, government policy, and foreign conditions constant, moves the economy down along the same AD curve to a point with higher real GDP demanded. 在收入预期、政府政策和国外环境不变的前提下，物价水平从 110 降到 105 只会使经济沿同一条 AD 曲线向下移动到需求更高的产出点。

Extension（拓展） Such movements reflect the combined effects of wealth, interest-rate, and international-trade channels previously discussed. 这类沿曲线移动反映的就是前文讨论的财富效应、利率效应和国际贸易效应的综合结果。

🔹Knowledge Point 2 — Shifts of the AD Curve（AD 曲线的平移）

Explanation（解释） If any variable other than the price level changes and affects the willingness of households, firms, or the government to spend, the entire AD curve shifts. 如果在物价水平不变的情况下，其他任何变量改变了家庭、企业或政府的支出意愿，则整条 AD 曲线会发生平移。

An increase in spending at every price level shifts AD to the right; a decrease in spending at every price level shifts AD to the left. 在每个物价水平上支出都增加时，AD 曲线整体右移；支出都减少时，AD 曲线整体左移。

Example（例子） If government purchases rise while the price level stays fixed, AD shifts to the right at all price levels. If firms become pessimistic about future profitability and cut investment, AD shifts to the left. 若在物价不变时政府采购支出增加，AD 在所有物价水平上都增加并整体右移；若企业对未来盈利前景悲观、减少投资，则 AD 整体左移。

Extension（拓展） Distinguishing between shifts and movements is crucial for understanding policy effects: monetary and fiscal policies typically aim to shift AD, not move the economy along a fixed AD curve. 区分“平移”和“沿曲线移动”对于理解政策效果非常关键：货币与财政政策通常是通过推动 AD 曲线平移来发挥作用，而不是让经济在既定 AD 曲线上移动。

🔹Knowledge Point 3 — Categories of AD Shifters（推动 AD 曲线平移的变量类别）

Explanation（解释） The main categories of variables that shift the aggregate demand curve are:

changes in government policies;
changes in the expectations of households and firms;
changes in foreign (external) variables. 推动 AD 曲线平移的主要变量包括： 1）政府政策的变化； 2）家庭和企业预期的变化； 3）国外（外部）因素的变化。

Example（例子） A tax cut (government policy), improved consumer confidence (expectations), or stronger foreign demand for domestic exports (foreign variable) can each shift AD to the right. 减税（政府政策）、消费者信心上升（预期）或国外对本国产品需求增强（外部因素）都可能使 AD 右移。

Extension（拓展） Later slides will analyze in detail how monetary and fiscal policies, expectations, and international conditions operate as AD shifters. 后续页面将详细分析货币与财政政策、预期以及国际环境如何具体地作为 AD 平移因素发挥作用。

本页小结（Summary） Price-level changes cause movements along a given AD curve, while changes in government policy, expectations, or foreign conditions shift the entire curve; understanding this distinction is fundamental for macro policy analysis. 物价水平的变化只会让经济在既定 AD 曲线上移动，而政府政策、预期或国外环境的变化会使整条 AD 曲线平移；理解这一差异是宏观政策分析的基础。

Slide 7 — Changes in Government Policies: Monetary and Fiscal Policy （第7页——政府政策变动：货币政策与财政政策）

Knowledge Points (知识点)

Monetary policy and its impact on aggregate demand（货币政策及其对总需求的影响）
Fiscal policy and its impact on aggregate demand（财政政策及其对总需求的影响）
How specific policy actions shift the AD curve right or left（具体政策如何使 AD 右移或左移）

🔹Knowledge Point 1 — Monetary Policy and Aggregate Demand（货币政策与总需求）

Explanation（解释） Monetary policy refers to actions taken by the central bank to manage the money supply and interest rates to achieve macroeconomic objectives such as high employment, price stability, economic growth, and financial stability. 货币政策是中央银行通过调节货币供给和利率，以实现高就业、物价稳定、经济增长和金融稳定等宏观目标的一系列行动。

By changing interest rates and credit conditions, monetary policy influences consumption and investment, thereby shifting the aggregate demand curve. 通过改变利率和信贷条件，货币政策会影响消费与投资，从而推动总需求曲线发生平移。

Example（例子） When the central bank reduces policy interest rates or conducts open-market purchases of bonds, market interest rates fall, lower borrowing costs, and encourage firms and households to spend more, shifting AD to the right. 当央行下调政策利率或在公开市场购买债券时，市场利率下降、借款成本降低，企业和家庭支出增加，AD 曲线右移。

Extension（拓展） Conversely, raising interest rates to fight inflation makes borrowing more expensive, reduces interest-sensitive spending, and shifts AD to the left. 相反，为抑制通胀而提高利率会使借款更昂贵，压缩对利率敏感的支出，使 AD 曲线左移。

🔹Knowledge Point 2 — Fiscal Policy and Aggregate Demand（财政政策与总需求）

Explanation（解释） Fiscal policy refers to changes in federal taxes and government purchases undertaken to achieve macroeconomic objectives. Because government purchases $G$ are part of aggregate demand, fiscal policy directly affects AD. 财政政策是政府通过调整税收和政府购买以实现宏观经济目标的政策；由于政府购买 $G$ 是总需求的一部分，财政政策会直接影响 AD。

An increase in government purchases shifts AD to the right; a decrease shifts AD to the left. 政府购买增加会使 AD 曲线右移，减少则会使 AD 左移。

Example（例子） If the government launches an infrastructure program and raises spending on roads and bridges, total spending in the economy increases at every price level, shifting AD to the right. 若政府启动基建计划、增加道路和桥梁支出，经济中在每个物价水平上的总支出都会提高，从而使 AD 右移。

Extension（拓展） Tax changes also affect AD through disposable income and after-tax profits:

Higher personal income taxes reduce disposable income, lower consumption, and shift AD left.
Lower personal income taxes raise disposable income, boost consumption, and shift AD right.
Higher business taxes reduce after-tax profits and investment, shifting AD left; lower business taxes do the opposite. 税收变化也会通过可支配收入和税后利润影响 AD：
个人所得税提高会压缩可支配收入、减少消费，使 AD 左移；
个人所得税降低会增加可支配收入、提升消费，使 AD 右移；
企业所得税提高会减少税后利润和投资，使 AD 左移；降低则相反。

🔹Knowledge Point 3 — Policy Mix and Direction of AD Shifts（政策组合与 AD 平移方向）

Explanation（解释） Both monetary and fiscal policies can be used in combination to stabilize the economy, either expanding aggregate demand during recessions or restraining it during periods of high inflation. 货币政策和财政政策可以配合使用，在经济衰退时扩大总需求，在高通胀时期抑制总需求，从而稳定经济。

Example（例子） During a recession, a central bank may cut interest rates while the government simultaneously increases spending or reduces taxes, producing a strong rightward shift of AD. 在衰退期间，央行可能降息，同时政府增加支出或减税，从而共同推动 AD 大幅右移。

Extension（拓展） However, inappropriate or poorly timed policies can overshoot, causing excessive inflation or crowding out private investment, so policymakers must carefully balance objectives and timing. 但如果政策力度或时机拿捏不当，也可能导致通胀过高或挤出私人投资，因此决策者必须在不同目标和时点之间做出谨慎权衡。

本页小结（Summary） Monetary policy shifts AD mainly by changing interest rates and credit conditions, while fiscal policy shifts AD through government spending and taxes; together they form powerful tools for moving the aggregate demand curve right or left. 货币政策主要通过改变利率和信贷条件来推动 AD 平移，财政政策则通过政府支出和税收来改变 AD；二者共同构成了使总需求曲线左移或右移的强有力政策工具。

Slide 8 — Expectations of Households and Firms （第8页——家庭与企业预期）

Knowledge Points (知识点)

Household income expectations and consumption（家庭对未来收入预期与消费）
Firms’ profitability expectations and investment（企业对未来盈利预期与投资）
Expectations as an aggregate demand shifter（预期作为总需求的平移因素）

🔹Knowledge Point 1 — Household Expectations and Consumption（家庭预期与消费）

Explanation（解释）
If households become more optimistic about their future incomes, they are likely to increase their current consumption, shifting the aggregate demand curve to the right.
如果家庭对未来收入更乐观，就更可能现在就增加消费，使总需求曲线向右移动。

If households become more pessimistic about their future incomes, they cut current consumption, shifting the aggregate demand curve to the left.
如果家庭对未来收入悲观，就会减少当前消费，使总需求曲线向左移动。

Example（例子）
Suppose people expect rapid wage growth next year due to a booming labor market; they may buy more cars and electronics now, increasing $C$ in $A D = C + I + G + NX$ and shifting AD to the right.
例如，人们预期明年劳动力市场火爆、工资大涨，就可能现在先多买汽车和电子产品，从而提高 $A D = C + I + G + NX$ 中的消费 $C$ ，推动 AD 右移。

Extension（拓展）
Expectations affect not only the level but also the timing of consumption: optimistic expectations pull future spending into the present, while pessimistic expectations push current spending into the future.
预期不仅影响消费总量，也影响消费时点：乐观预期会把未来消费“拉到现在”，悲观预期则会把当前消费“推到未来”。

🔹Knowledge Point 2 — Firms’ Expectations and Investment（企业预期与投资）

Explanation（解释）
If firms become more optimistic about the future profitability of investment spending, the aggregate demand curve will shift to the right because investment $I$ increases at every price level.
如果企业对投资的未来盈利能力更加乐观，企业在任何物价水平下都会增加投资 $I$ ，从而使总需求曲线右移。

If firms become more pessimistic, they cut back investment, shifting the aggregate demand curve to the left.
如果企业更悲观，就会减少投资，使总需求曲线向左移动。

Example（例子）
A new technology that promises high future returns may lead firms to build more factories and buy more equipment, increasing investment today and shifting AD rightward.
一种预示未来高回报的新技术，可能促使企业现在就多建工厂、多买设备，从而增加当前投资并推动 AD 右移。

Extension（拓展）
Business surveys of “confidence” or “sentiment” are often used as indicators of future investment and thus as leading indicators of movements in aggregate demand.
商业信心或景气指数等调查经常被用作预测未来投资的指标，因此也是观察总需求变化的重要先行指标。

🔹Knowledge Point 3 — Expectations as AD Shifters（预期作为总需求平移因素）

Explanation（解释）
Changes in expectations of households and firms are non-price factors; they shift the entire AD curve rather than cause a movement along it.
家庭和企业预期的变化属于“非价格因素”，会导致整条 AD 曲线平移，而不是在原曲线上移动。

Example（例子）
Even if the price level stays constant, a sudden loss of confidence due to a financial crisis can reduce both consumption and investment, moving AD leftward and potentially triggering a recession.
即使物价水平不变，若因金融危机导致信心骤降，消费和投资都会下降，使 AD 左移并可能引发衰退。

Extension（拓展）
Because expectations can change quickly, they are an important source of short-run fluctuations in real GDP and employment.
由于预期可以在短期内迅速变化，它们是造成实际 GDP 和就业短期波动的重要来源。

本页小结（Summary）
Optimistic expectations of income and profit shift AD to the right by raising current consumption and investment, while pessimistic expectations shift AD to the left, making expectations a key non-price determinant of aggregate demand.
乐观的收入与盈利预期通过提高当前消费和投资使 AD 右移，悲观预期则使 AD 左移，因此预期是影响总需求的重要非价格决定因素。

Slide 9 — Changes in Foreign Variables （第9页——国外变量的变化）

Knowledge Points (知识点)

Foreign demand for domestic goods and domestic demand for foreign goods（国外对本国产品需求与本国对外国商品需求）
Domestic GDP growth relative to foreign GDP growth（本国 GDP 增长相对于外国增长）
Exchange rate changes and net exports（汇率变化与净出口）

🔹Knowledge Point 1 — Foreign Demand and Domestic Demand for Imports（国外需求与本国进口需求）

Explanation（解释）
If households and firms in other countries buy fewer U.S. (domestic) goods, or if households and firms at home buy more foreign goods, net exports fall and the aggregate demand curve shifts to the left.
如果外国的家庭和企业减少购买美国（本国）商品，或者本国的家庭和企业更多购买外国商品，净出口就会下降，总需求曲线左移。

Example（例子）
A recession in Europe can reduce European demand for U.S. exports, while U.S. consumers may continue buying European products; net exports $NX$ decline and AD shifts left.
例如，欧洲经济衰退会减少欧洲对美国出口的需求，而美国消费者可能仍然购买欧洲产品；净出口 $NX$ 下降，AD 左移。

Extension（拓展）
Globalization means that domestic demand is closely tied to foreign business cycles; shocks abroad can significantly influence domestic aggregate demand through trade.
在全球化背景下，本国需求与外国商业周期紧密相连，国外冲击可以通过贸易渠道显著影响本国总需求。

🔹Knowledge Point 2 — Relative GDP Growth and Net Exports（相对 GDP 增长与净出口）

Explanation（解释）
If real GDP in the United States increases faster than real GDP in other countries, U.S. imports will increase faster than U.S. exports, and net exports will fall, shifting AD to the left.
如果美国实际 GDP 增长快于其他国家，美国进口的增长会快于出口增长，净出口下降，从而使 AD 左移。

Example（例子）
When the U.S. economy grows rapidly while trading partners grow slowly, U.S. consumers buy more foreign goods, but foreigners’ incomes do not grow enough to increase their purchases of U.S. goods by the same amount.
当美国经济快速增长而贸易伙伴增长缓慢时，美国消费者会多买外国商品，但外国收入增长不足以同幅度增加对美国产品的购买。

Extension（拓展）
Conversely, if foreign economies grow faster than the domestic economy, foreign demand for domestic exports may rise more quickly than domestic demand for imports, increasing $NX$ and shifting AD to the right.
反之，如果外国经济增长快于本国经济，外国对本国出口的需求可能增长得比本国对进口的需求更快，从而增加 $NX$ 、推动 AD 右移。

🔹Knowledge Point 3 — Exchange Rate Changes and AD（汇率变化与总需求）

Explanation（解释）
Net exports will also fall if the exchange rate between the dollar and foreign currencies rises (domestic currency appreciates). Domestic goods become more expensive in foreign currencies, while foreign goods become cheaper in domestic currency.
如果本币相对于外币升值（例如美元对外币汇率上升），净出口也会下降：本国产品以外币计价更贵，而外国商品以本币计价更便宜。

Example（例子）
Suppose initially $1 = €1$ . A $20 Blu-ray disc exported from the U.S. to France costs €20, and a €50 bottle of French wine costs $50 in the U.S.
假设最初 $1 = €1$ ，那么一张从美国出口到法国的 20 美元蓝光碟价格为 20 欧元，一瓶 50 欧元的法国葡萄酒在美国售价为 50 美元。

If the exchange rate rises to $1 = €1.50$ , the disc’s euro price rises from €20 to €30, discouraging French buyers, while the wine’s dollar price falls from $50 to about $33.33, encouraging U.S. buyers.
如果汇率升至 $1 = €1.50$ ，蓝光碟在法国的价格从 20 欧元涨到 30 欧元，法国消费者会减少购买；而法国葡萄酒在美国的美元价格从 50 美元降到约 33.33 美元，美国人会多买。

As a result, U.S. exports fall, U.S. imports rise, and the aggregate demand curve shifts to the left.
结果是美国出口减少、进口增加，总需求曲线左移。

Extension（拓展）
An increase in net exports at every price level shifts AD to the right; net exports will increase if domestic GDP grows more slowly than foreign GDP or if the domestic currency depreciates against other currencies.
若在每个物价水平上净出口都增加，AD 曲线会右移；当本国 GDP 增长慢于外国或本币相对其他货币贬值时，净出口往往会上升。

本页小结（Summary）
Foreign demand, relative GDP growth, and exchange rate movements change net exports and thus shift aggregate demand; stronger net exports shift AD to the right, while weaker net exports shift it to the left.
国外需求、相对 GDP 增长和汇率变动会改变净出口，从而推动总需求平移；净出口增强使 AD 右移，净出口减弱则使 AD 左移。

Slide 10 — Summary of Factors Shifting the AD Curve （第10页——推动总需求曲线平移的因素总结）

Knowledge Points (知识点)

Domestic policy variables: interest rates, government purchases, taxes（国内政策变量：利率、政府购买与税收）
Expectations of households and firms（家庭与企业预期）
Foreign variables: foreign GDP growth and exchange rates（国外变量：外国 GDP 增长与汇率）

🔹Knowledge Point 1 — Policy Variables and AD Shifts（政策变量与 AD 平移）

Explanation（解释）
From the summary table, an increase in:

interest rates shifts AD to the left;
government purchases shifts AD to the right;
personal income taxes or business taxes shifts AD to the left.
概括表格可知：
利率上升使 AD 左移；
政府购买增加使 AD 右移；
个人或企业税收增加使 AD 左移。

Example（例子）
Higher interest rates raise borrowing costs and reduce consumption and investment; higher personal income taxes reduce disposable income and consumption; higher business taxes reduce after-tax profits and investment.
较高利率提高借款成本、压低消费与投资；较高个人所得税压缩可支配收入、降低消费；较高企业税收减少税后利润、打击投资。

Extension（拓展）
The table’s small AD graphs illustrate these effects: arrows pointing left show contractionary influences (lower real GDP at each price level), while arrows pointing right show expansionary influences.
表格中小图的箭头方向直观表示这些效果：向左箭头代表紧缩效应（每个物价水平下的实际 GDP 减少），向右箭头代表扩张效应。

Image/Data Analysis（图像或数据分析）
In the left panel of the table, higher interest rates or higher taxes are associated with a leftward shift from $A D_{1}$ to $A D_{2}$ ; higher government purchases are associated with a rightward shift from $A D_{1}$ to $A D_{2}$ .
在表格左半部分中，利率或税收上升对应 $A D_{1}$ 向 $A D_{2}$ 左移，政府购买增加则对应 $A D_{1}$ 向 $A D_{2}$ 右移。

🔹Knowledge Point 2 — Expectations as Shown in the Table（表格中的预期因素）

Explanation（解释）
An increase in households’ expectations of their future incomes shifts the AD curve to the right because consumption spending increases.
家庭对未来收入预期提高会增加消费支出，从而使 AD 曲线右移。

Similarly, an increase in firms’ expectations of the future profitability of investment spending shifts AD to the right because investment increases.
同理，企业对未来投资盈利能力更乐观时，投资增加，也会推动 AD 右移。

Example（例子）
The table’s panel on households shows a rightward arrow from $A D_{1}$ to $A D_{2}$ , indicating higher real GDP demanded at each price level when households become more optimistic.
表格中关于家庭预期的小图中，箭头从 $A D_{1}$ 指向 $A D_{2}$ ，表示在每个物价水平下，当家庭更乐观时需求的实际 GDP 更高。

Extension（拓展）
Negative shocks to expectations—such as financial crises or sudden political instability—would reverse the arrow, shifting AD left as both $C$ and $I$ fall.
若遇到金融危机或政治动荡等负面预期冲击，箭头就会反向，因消费和投资下降而使 AD 左移。

Image/Data Analysis（图像或数据分析）
The expectation row in the table visually groups these factors with the same rightward arrow, emphasizing that both household and firm optimism are expansionary for aggregate demand.
表格中预期这一行的小图都带有向右箭头，强调家庭和企业乐观预期对总需求具有共同的扩张作用。

🔹Knowledge Point 3 — Foreign Variables in the Summary Table（表格中的国外变量）

Explanation（解释）
The table also lists two key foreign variables:

the growth rate of domestic GDP relative to foreign GDP;
the exchange rate (value of the domestic currency) relative to foreign currencies.
表格还列出了两个关键国外变量：
本国 GDP 增长率相对于外国的增长率；
本币相对于外币的汇率水平。

An increase in the domestic GDP growth rate relative to foreign growth shifts AD to the left because imports rise faster than exports, reducing net exports.
如果本国 GDP 增速相对外国提高，进口会比出口增加得更快，净出口下降，使 AD 左移。

An increase in the exchange rate (domestic currency appreciation) also shifts AD to the left because imports rise and exports fall.
本币汇率上升（升值）同样会使 AD 左移，因为进口增加、出口减少。

Example（例子）
The right panel of the table shows $A D_{2}$ to the left of $A D_{1}$ for both higher relative GDP growth and a stronger domestic currency, indicating a reduction in real GDP demanded at each price level.
在表格右半部分中，较高的相对 GDP 增速和本币升值这两行的小图都显示 $A D_{2}$ 位于 $A D_{1}$ 左侧，表明每个物价水平下需求的实际 GDP 减少。

Extension（拓展）
Conversely, if domestic GDP grows more slowly than foreign GDP or if the domestic currency depreciates, net exports increase and AD shifts to the right; the arrow direction would reverse in that case.
反之，若本国 GDP 增速低于外国或本币贬值，净出口会上升，AD 将右移，箭头方向与表中相反。

Image/Data Analysis（图像或数据分析）
The arrows in these rows help connect foreign variables to net exports: leftward arrows represent situations where imports rise faster than exports or exports fall due to appreciation, both cutting $NX$ .
这些行中的箭头把国外变量与净出口联系起来：向左箭头代表进口增长快于出口或因本币升值导致出口下降，两者都会压缩 $NX$ 。

本页小结（Summary）
The summary table organizes policy variables, expectations, and foreign factors and shows how each one shifts the AD curve right or left; together they provide a complete map of the main determinants of aggregate demand.
该总结表将政策变量、预期与国外因素系统地归类，并展示每一项如何使 AD 曲线右移或左移，为总需求的主要决定因素提供了一幅完整的“地图”。

Slide 11 — Aggregate Supply: Learning Objective （第11页——总供给：学习目标）

Knowledge Points (知识点)

Definition of aggregate supply（总供给的定义）
Short run vs. long run in aggregate supply（总供给中的短期与长期区别）
Learning objective: determinants and movements vs. shifts（学习目标：决定因素与曲线移动/平移）

🔹Knowledge Point 1 — Definition of Aggregate Supply（总供给的定义）

Explanation（解释）
Aggregate supply shows the effect of changes in the price level on the quantity of goods and services that firms are willing and able to supply.
总供给描述的是物价水平变化，对企业愿意且能够提供的商品与服务数量的影响关系。

Example（例子）
If the overall price level rises while many costs are fixed in the short run, firms may find production more profitable and increase their output; this higher quantity supplied is part of aggregate supply.
如果总体物价水平上升而许多成本在短期内固定不变，企业会发现生产更有利可图，从而增加产出；这种增加的供给量就是总供给的一部分。

Extension（拓展）
Aggregate supply relates the price level $P$ to real GDP supplied $Y^{S}$ for the whole economy, not just for one industry or one firm.
总供给把整个经济体系中的物价水平 $P$ 与所提供的实际产出 $Y^{S}$ 联系起来，而不是只看某一个行业或企业。

🔹Knowledge Point 2 — Short Run vs. Long Run in Aggregate Supply（总供给中的短期与长期）

Explanation（解释）
The effect of changes in the price level on aggregate supply is very different in the short run compared with the long run.
物价水平变化对总供给的影响，在短期与长期是截然不同的。

Therefore, economists use two aggregate supply curves: one for the short run (SRAS) and one for the long run (LRAS).
因此，我们需要使用两条总供给曲线：一条是短期总供给曲线（SRAS），一条是长期总供给曲线（LRAS）。

Example（例子）
In the short run, wages and some input prices are “sticky,” so a higher price level can increase profits and output. In the long run, wages and prices fully adjust, so changes in $P$ do not change the natural level of real GDP.
短期内，工资和一些投入价格具有粘性，因此物价上升可以提高利润、增加产出；而在长期中，工资和价格都能完全调整，因此 $P$ 的变化不会改变实际 GDP 的自然水平。

Extension（拓展）
Short-run movements along SRAS explain business cycles, while shifts in LRAS reflect long-run economic growth driven by factors like labor, capital, and technology.
沿着 SRAS 的短期变动解释的是商业周期，而 LRAS 的平移反映的是由劳动力、资本和技术等因素推动的长期经济增长。

🔹Knowledge Point 3 — Learning Objective for Aggregate Supply（总供给部分的学习目标）

Explanation（解释）
The learning objective is to identify the determinants of aggregate supply and distinguish between a movement along the short-run aggregate supply curve and a shift of the curve.
本章学习目标是识别总供给的决定因素，并区分“沿短期总供给曲线的移动”和“短期总供给曲线的整体平移”。

Example（例子）
A change in the price level causes a movement along SRAS, whereas a change in technology or the labor force shifts SRAS or LRAS.
物价水平的变化只会使经济沿 SRAS 曲线移动；而技术或劳动力数量的变化则会使 SRAS 或 LRAS 曲线整体平移。

Extension（拓展）
Understanding these differences is crucial for analyzing how cost shocks, productivity growth, and policy changes affect inflation and output.
理解这些差异对于分析成本冲击、生产率增长以及政策变化如何影响通胀和产出非常关键。

本页小结（Summary）
Aggregate supply links the price level to the quantity of output firms provide, and we use separate short-run and long-run supply curves to capture very different behaviors; our goal is to understand their determinants and how movements differ from shifts.
总供给将物价水平与企业提供的产出数量联系起来，我们用短期与长期两条曲线来刻画截然不同的行为；学习目标是弄清这些曲线的决定因素，以及“沿曲线移动”和“曲线平移”的区别。

Slide 12 — The Long-run Aggregate Supply Curve （第12页——长期总供给曲线）

Knowledge Points (知识点)

Determinants of long-run real GDP（长期实际 GDP 的决定因素）
Potential GDP and full-employment GDP（潜在 GDP 与充分就业产出）
Shape and meaning of the LRAS curve（LRAS 曲线的形状及含义）

🔹Knowledge Point 1 — Determinants of Long-run Real GDP（长期实际 GDP 的决定因素）

Explanation（解释）
In the long run, the level of real GDP is determined by the number of workers, the capital stock (factories, office buildings, machinery, and equipment), and available technology.
从长期来看，实际 GDP 的水平由劳动力数量、资本存量（工厂、办公楼、机器设备）以及可用技术决定。

Changes in the price level do not change these fundamentals in the long run, so they do not affect long-run real GDP.
在长期中，物价水平的变化不会改变这些基本要素，因此不会改变长期的实际 GDP 水平。

Example（例子）
If an economy doubles its number of skilled workers and improves technology, its potential output rises even if the price level stays the same.
如果一个经济体的熟练工人数量翻倍、技术进步，即使物价水平不变，其潜在产出也会上升。

Extension（拓展）
These determinants are often summarized as long-run aggregate supply depending on factor inputs and technology:
$Y^{L R} = F (L, K, A)$ ,
where $L$ is labor, $K$ is capital, and $A$ is technology.
通常我们用一个长期生产函数概括长期总供给：
$Y^{L R} = F (L, K, A)$ ，其中 $L$ 为劳动， $K$ 为资本， $A$ 为技术。

🔹Knowledge Point 2 — Potential GDP and Full Employment（潜在 GDP 与充分就业）

Explanation（解释）
The level of real GDP in the long run is called potential GDP or full-employment GDP.
长期实际 GDP 的水平被称为潜在 GDP，也叫充分就业产出。

At potential GDP, firms operate at their normal capacity, and everyone who wants a job can find one, except the structurally and frictionally unemployed.
在潜在 GDP 下，企业处于正常产能水平，除结构性和摩擦性失业者外，任何想工作的人都能找到工作。

Example（例子）
Potential GDP corresponds to the output level where unemployment is at the “natural rate”—for example, around 4–5% in many advanced economies.
潜在 GDP 对应于失业率处于“自然失业率”附近的产出水平，例如许多发达经济体大约 4–5% 的失业率。

Extension（拓展）
Temporary booms can push actual GDP above potential, but this usually leads to rising inflation and cannot be sustained without further growth in $L$ , $K$ , or $A$ .
短期繁荣可以把实际 GDP 推到潜在水平之上，但往往伴随通胀上升，而且如果 $L$ 、 $K$ 或 $A$ 不再增长，这种状态无法长期维持。

🔹Knowledge Point 3 — Shape and Interpretation of LRAS（LRAS 曲线的形状与含义）

Explanation（解释）
The long-run aggregate supply (LRAS) curve shows the relationship between the price level and the quantity of real GDP supplied in the long run.
长期总供给曲线（LRAS）表现的是长期中物价水平与实际 GDP 供给量之间的关系。

Because changes in the price level do not affect long-run real GDP, the LRAS curve is vertical at potential GDP.
由于物价水平变化不会改变长期实际 GDP，LRAS 曲线在潜在 GDP 的位置是一条垂直线。

Example（例子）
In 2019, suppose the price level was 112 and potential GDP was $18.9 trillion. If the price level had been 102 or 122 instead, long-run aggregate supply would still have been $18.9 trillion along the same vertical LRAS line.
例如，2019 年物价水平为 112、潜在 GDP 为 18.9 万亿美元；即使物价水平是 102 或 122，长期总供给仍然是同一垂直 LRAS 线上 18.9 万亿美元的水平。

Extension（拓展）
A vertical LRAS means that in the long run, aggregate demand affects only the price level, not real output; long-run growth must come from supply-side factors.
LRAS 垂直意味着从长期来看，总需求只能影响物价水平而不能改变实际产出；长期经济增长必须来自供给侧因素。

本页小结（Summary）
Long-run real GDP is determined by labor, capital, and technology, giving rise to a vertical LRAS at potential GDP, so long-run output is independent of the price level.
长期实际 GDP 由劳动、资本和技术决定，对应一条在潜在产出处的垂直 LRAS 曲线，因此长期产出不受物价水平影响。

Slide 13 — Shifts of the Long-run Aggregate Supply Curve （第13页——长期总供给曲线的平移）

Knowledge Points (知识点)

Reasons why LRAS shifts over time（LRAS 随时间平移的原因）
Link between potential GDP growth and LRAS rightward shifts（潜在 GDP 增长与 LRAS 右移）
Graphical interpretation of LRAS shifts（LRAS 平移的图像解读）

🔹Knowledge Point 1 — Why LRAS Shifts Over Time（LRAS 随时间平移的原因）

Explanation（解释）
Figure 23.2 shows that the LRAS curve shifts to the right each year because potential GDP increases over time.
图 23.2 显示，长期总供给曲线每年都会向右移动，因为潜在 GDP 随时间不断增加。

This shift occurs as the number of workers increases, the economy accumulates more machinery and equipment, and technological change takes place.
这种平移是由于劳动力数量增加、经济积累更多机器和设备以及技术进步等因素共同作用的结果。

Example（例子）
When a growing population enters the labor force and firms invest in new capital goods, the economy can sustainably produce more output at full employment.
当劳动力人口不断增加、企业投资新的资本设备时，经济就能在充分就业状态下持续生产更多产出。

Extension（拓展）
Structural reforms that improve education, infrastructure, or innovation capacity can also shift LRAS to the right by raising productivity.
改善教育、基础设施或创新能力的结构性改革也会通过提高生产率，使 LRAS 曲线右移。

🔹Knowledge Point 2 — Potential GDP Growth and LRAS Rightward Shift（潜在 GDP 增长与 LRAS 右移）

Explanation（解释）
Figure 23.2 shows potential GDP increasing from $18.9 trillion in 2019 to $19.3 trillion in 2020 and to $19.7 trillion in 2021 (in 2012 dollars).
图 23.2 表明，按 2012 年不变价计算的潜在 GDP 从 2019 年的 18.9 万亿美元增加到 2020 年的 19.3 万亿，再到 2021 年的 19.7 万亿。

Each increase in potential GDP corresponds to a rightward shift of the vertical LRAS curve.
每一次潜在 GDP 的上升，都对应一条垂直 LRAS 曲线向右平移。

Example（例子）
$L R A S_{2019}$ is vertical at 18.9, $L R A S_{2020}$ at 19.3, and $L R A S_{2021}$ at 19.7; these parallel vertical lines show the economy’s expanding full-employment capacity.
$L R A S_{2019}$ 垂直于 18.9， $L R A S_{2020}$ 垂直于 19.3， $L R A S_{2021}$ 垂直于 19.7，这些平行的垂直线展示了经济充分就业产能的扩张。

Extension（拓展）
The average growth rate implied by these numbers reflects long-run supply-side growth; higher growth economies experience faster rightward shifts of LRAS.
这些数字隐含的平均增长率反映的是供给侧长期增长；增长较快的经济体，其 LRAS 右移的速度也更快。

🔹Knowledge Point 3 — Image/Data Analysis of LRAS Shifts（LRAS 平移的图像与数据分析）

Explanation（解释）
In the figure, the vertical axis shows the price level (GDP deflator, 2012 = 100), while the horizontal axis shows real GDP.
图中纵轴表示物价水平（以 2012 年为 100 的 GDP 平减指数），横轴表示实际 GDP。

The three LRAS lines are parallel and vertical, indicating that for each year, real GDP supplied in the long run is fixed at that year’s potential GDP, regardless of price level.
三条 LRAS 线互相平行且垂直，表示在每一年内，长期供给的实际 GDP 固定在当年的潜在 GDP 水平，与物价水平无关。

Image/Data Analysis（图像或数据分析）
Arrows along the horizontal axis from 18.9 → 19.3 → 19.7 show the rightward shift in potential GDP, while double-headed arrows along the price axis (102–112–122) illustrate that LRAS does not change when the price level changes within a given year.
横轴上从 18.9→19.3→19.7 的箭头体现潜在 GDP 的右移；纵轴上 102–112–122 的双向箭头表明在同一年中，即使物价水平在这个区间变动，LRAS 也不会移动。

Extension（拓展）
This figure visually separates short-run movements in the price level (vertical changes) from long-run growth in the economy’s capacity (horizontal shifts of LRAS).
该图形直观地区分了物价在短期内的上下波动（纵向变化）和经济产能在长期内的增长（LRAS 的横向平移）。

本页小结（Summary）
LRAS shifts right over time as potential GDP grows due to more labor, capital, and better technology; graphically this appears as parallel vertical lines moving right along the real GDP axis.
随着劳动力、资本和技术的提升，潜在 GDP 增长，使 LRAS 随时间向右平移；图像上表现为一组沿实际 GDP 轴向右移动的平行垂直线。

Slide 14 — The Short-run Aggregate Supply Curve （第14页——短期总供给曲线）

Knowledge Points (知识点)

Upward slope of the SRAS curve（SRAS 曲线为何向上倾斜）
Reasons firms produce more when prices rise（价格上升时企业为何扩大产出）
Role of imperfect price-level expectations（价格预期误差的作用）

🔹Knowledge Point 1 — Upward-sloping SRAS Curve（SRAS 曲线向上倾斜）

Explanation（解释）
While the LRAS curve is vertical, the short-run aggregate supply (SRAS) curve is upward sloping because, over the short run, as the price level increases, the quantity of goods and services firms are willing to supply increases.
长期总供给曲线 LRAS 是垂直的，而短期总供给曲线 SRAS 向上倾斜，这是因为在短期内，物价水平上升会促使企业愿意提供更多商品和服务。

Example（例子）
When the overall price level rises faster than firms’ costs, profits increase and firms respond by raising output, which shows up as a movement upward along the SRAS curve.
当总体物价水平上升的速度快于企业成本时，利润增加，企业会扩大产出，这在图上表现为沿 SRAS 曲线向上移动。

Extension（拓展）
The upward slope is a key reason why increases in aggregate demand in the short run lead to both higher output and higher prices (demand-pull inflation).
SRAS 向上倾斜是解释短期内总需求增加为何既提高产出又推高物价（需求拉动型通胀）的重要原因。

🔹Knowledge Point 2 — Why Firms Produce More When Prices Rise（价格上升时企业为何多生产）

Explanation（解释）
Input prices adjust slowly: output prices can rise faster than wages and other input costs, so firms’ profits increase and they raise production.
投入品价格调整较慢：产品价格上涨的速度往往快于工资和其他成本，企业利润因此增加，于是扩大生产。

Sticky prices: some firms adjust their prices slowly; when the overall price level rises, their goods temporarily become cheaper relative to competitors, so sales and production rise.
价格粘性：有些企业调价很慢，当总体物价水平上升时，它们的产品相对竞争对手暂时“更便宜”，销量和产量都会上升。

Example（例子）
If wages are fixed in yearly contracts but the prices of finished goods increase unexpectedly, firms’ profit margins rise in the short run, encouraging them to schedule overtime or hire more workers.
如果工资在年度合同中锁定，而成品价格意外上升，短期内企业利润率提高，就会安排加班或多雇工人。

Extension（拓展）
Over time, as input contracts are renegotiated and slow adjusters update their prices, these profit advantages disappear, pushing the economy back towards potential GDP and LRAS.
随着时间推移，投入合同会重新谈判，价格调整缓慢的企业也会更新价格，这些利润优势就会消失，经济会逐渐回到潜在 GDP 与 LRAS 附近。

🔹Knowledge Point 3 — Imperfect Price-level Expectations（价格预期误差与 SRAS）

Explanation（解释）
Most economists believe that the key explanation for an upward-sloping SRAS is that workers and firms cannot perfectly predict the future price level.
多数经济学家认为，SRAS 向上倾斜的根本原因在于劳动者和企业无法完美预测未来的物价水平。

If predictions were perfect, wages and prices would adjust immediately, and SRAS would be vertical like LRAS.
如果预期完全准确，工资与价格会立刻调整，SRAS 也会像 LRAS 一样垂直。

Example（例子）
When firms expect a price level of 110 but actual prices turn out to be 115, they agreed to wage contracts based on 110, so real wages are lower than expected and firms hire more labor and expand output.
如果企业原本预期物价水平为 110，而实际物价达到 115，它们签订的工资合同是基于 110 的预期，结果实际工资比预期低，企业就会多雇佣劳动、扩大产出。

Extension（拓展）
The failure to predict the price level accurately creates short-run misalignments of real wages and prices, generating movements along SRAS; as expectations adjust, SRAS may shift and the economy moves back toward long-run equilibrium.
价格预期误差在短期内造成实际工资和价格的错位，从而在 SRAS 上产生变动；随着预期修正，SRAS 可能会平移，经济也会回到长期均衡。

本页小结（Summary）
SRAS slopes upward because input prices adjust slowly and firms mispredict the price level, so higher prices temporarily raise profits and output; with perfect adjustment, SRAS would become vertical like LRAS.
由于投入价格调整缓慢和价格预期误差，物价上升会在短期内提高企业利润并推动产出，使 SRAS 向上倾斜；如果所有价格能立刻完全调整，SRAS 也会像 LRAS 一样变成垂直线。

Slide 15 — Sticky Wages and Prices: Contracts （第15页——工资与价格粘性：合同因素）

Knowledge Points (知识点)

Three main reasons for wage and price stickiness（三大导致工资和价格粘性的原因）
Definition of “sticky” wages and prices（“粘性”工资与价格的定义）
How long-term contracts create stickiness and affect SRAS（长期合同如何造成粘性并影响 SRAS）

🔹Knowledge Point 1 — Three Reasons for Stickiness（三大粘性原因）

Explanation（解释）
There are three main reasons why wages and prices are “sticky” in the short run:

Contracts make some wages and prices sticky;
Firms are often slow to adjust wages;
Menu costs make some prices sticky.
工资和价格在短期内具有“粘性”的三大原因是：
1）合同使部分工资和价格固定不变；
2）企业往往缓慢调整工资；
3）菜单成本使部分价格难以及时调整。

Example（例子）
For many workers, wages are determined in multi-year labor contracts; for many goods, prices are printed in catalogs or menus and cannot be changed daily.
很多工人的工资由多年期劳动合同决定；许多商品的价格印在目录或菜单上，不能每天随意更改。

Extension（拓展）
Because these frictions prevent costs and prices from fully adjusting, unexpected changes in the overall price level can temporarily increase or reduce firms’ profit margins, leading to movements along SRAS.
由于这些摩擦阻止成本和价格完全调整，当总体物价意外变化时，企业的利润率会暂时上升或下降，从而在 SRAS 曲线上产生调整。

🔹Knowledge Point 2 — What “Sticky” Wages and Prices Mean（“粘性”工资与价格的含义）

Explanation（解释）
Prices or wages are said to be “sticky” when they do not respond quickly to changes in demand or supply.
当工资或价格对需求或供给的变化反应缓慢时，我们就说它们具有“粘性”。

Contracts can lock in nominal wages or prices for a period of time, so even if market conditions change, the contracted wage or price remains fixed.
合同可以在一定时期内锁定名义工资或价格，即使市场状况发生变化，合同中的工资或价格仍保持不变。

Example（例子）
A two-year lease fixes the rent for an office; if demand for office space rises and market rents increase, the lease payment does not change until the contract expires.
一份两年期的写字楼租约会在合同期内固定租金；即使办公需求增加、市场租金上升，租约中约定的租金也要等合同到期后才能调整。

Extension（拓展）
Sticky nominal wages and prices imply that in the short run, real wages and relative prices can deviate from what firms and workers expected, creating incentives to change output instead of instantly renegotiating all contracts.
名义工资和价格的粘性意味着短期内实际工资和相对价格会偏离企业和工人的预期，从而促使企业先调整产出，而不是立即重新谈判所有合同。

🔹Knowledge Point 3 — Contracts, Profits, and SRAS（合同、利润与 SRAS）

Explanation（解释）
Contracts make some wages and prices fixed; when the overall price level rises unexpectedly, firms can raise the prices they charge while some wage costs remain fixed by contract, increasing profits and output.
合同使部分工资和价格固定；当总体物价意外上升时，企业可以提高产品价格，而部分工资成本仍被合同锁定，从而提高利润并扩大产出。

Example（例子）
Delta Air Lines signs a three-year contract with the pilots’ union during a recession when ticket sales are low. Later, the economy expands and ticket demand rises, so Delta raises ticket prices, but pilot wages remain fixed by contract. Flying more passengers becomes profitable, so Delta increases output (flights).
例如，达美航空在经济衰退、机票销售低迷时与飞行员工会签三年合同。之后经济复苏、机票需求增加，达美提高票价，而飞行员工资仍按合同固定，从而飞更多乘客变得更有利可图，公司就会增加航班数量。

Extension（拓展）
This mechanism illustrates why an unexpected rise in the price level leads to higher output in the short run—one of the reasons SRAS slopes upward.
这一机制说明了为什么意外的物价上升会在短期内提高产出，也是 SRAS 曲线向上倾斜的原因之一。

本页小结（Summary）
Wages and prices are sticky in the short run mainly because of contracts, slow wage adjustment, and menu costs; these rigidities mean that unexpected price changes can raise profits and output, contributing to an upward-sloping SRAS.
短期内工资与价格之所以具有粘性，主要是由于合同、工资调整缓慢和菜单成本；这些刚性使得意外的物价变动会提高利润与产出，从而促成 SRAS 曲线向上倾斜。

Knowledge Points (知识点)

Firms are often slow to adjust wages（企业调整工资往往较慢）
Effects of slow wage adjustment on SRAS（工资调整缓慢对 SRAS 的影响）
Menu costs and sticky product prices（菜单成本与产品价格粘性）

🔹Knowledge Point 1 — Firms Are Slow to Adjust Wages（企业工资调整缓慢）

Explanation（解释）
Many union workers have wages fixed by contract for several years, and many nonunion workers have wages adjusted only once a year.
许多工会工人的工资由多年合同固定，许多非工会工人的工资也往往一年只调整一次。

Because of this, when the general price level changes, nominal wages do not immediately change to keep real wages constant.
因此，当总体物价水平变化时，名义工资不会立刻相应调整来保持实际工资不变。

Example（例子）
Suppose you accept a job in June at a salary of 45,000 dollars per year; your firm will probably not adjust your salary until the following June, even if it later discovers that prices are higher or lower than expected.
例如，你在 6 月以每年 45,000 美元的工资入职，这家企业很可能要到下一年 6 月才会重新调整工资，即便后来发现物价比预期高或低。

Extension（拓展）
This lag in wage adjustment means that in the short run, a rise in the price level reduces real wages and makes hiring more workers profitable; a fall in the price level raises real wages and makes hiring less profitable.
工资调整的滞后意味着在短期内，物价上升会降低实际工资、提高雇佣更多劳动的盈利性，而物价下降则会提高实际工资、降低雇佣的盈利性。

🔹Knowledge Point 2 — Wage Stickiness and SRAS（工资粘性与 SRAS）

Explanation（解释）
If firms are slow to adjust wages, a rise in the price level increases the profitability of hiring more workers and producing more output; a fall in the price level decreases profitability and reduces output.
如果企业缓慢调整工资，物价水平上升会提高雇佣更多工人和扩大产出的盈利性；物价水平下降则会降低盈利性、减少产出。

This provides another explanation for why the short-run aggregate supply curve slopes upward.
这再次解释了为什么短期总供给曲线向上倾斜。

Example（例子）
When inflation unexpectedly rises from 2% to 5%, but nominal wages are fixed for the year, the real cost of labor falls; firms respond by expanding hours and production.
如果通胀率意外从 2% 升至 5%，而名义工资在这一年固定不变，那么劳动的实际成本下降，企业就会通过加班等方式扩大产出。

Extension（拓展）
Over time, as wage contracts are renegotiated to reflect higher prices, real wages are restored and the short-run boost to output disappears, moving the economy back toward potential GDP.
随着时间推移，当工资合同在续签时会将更高的物价水平计入其中，实际工资恢复，短期产出扩张的效果消失，经济回到潜在 GDP 附近。

Explanation（解释）
Firms set today’s prices partly based on what they expect future prices and costs (wages, rent, ingredients, demand) to be. Changing prices is costly—printing new menus, re-tagging shelves, updating websites—these costs are called menu costs.
企业在定价时部分依据对未来价格和成本（工资、房租、原料、需求）的预期。改变价格本身具有成本，如重新印菜单、改价签、更新网站，这些被称为“菜单成本”。

When the price level rises unexpectedly, firms want to raise prices, but some do not adjust immediately because of menu costs. Their unchanged prices become relatively lower, increasing demand for their products and encouraging higher output.
当总体物价意外上升时，企业希望提价，但有些企业因为菜单成本而不会立刻调整价格，它们的价格在相对意义上变得更低，从而增加产品需求并促进更高产出。

Example（例子）
A restaurant facing higher food costs might delay raising menu prices because reprinting menus is expensive; in the meantime, as other restaurants raise prices, its meals become relatively cheap and attract more customers.
例如，一家餐厅面对食品成本上升却因为重印菜单昂贵而延迟提价；在此期间，其他餐厅已经涨价，它的餐食就显得相对便宜，从而吸引更多顾客。

Extension（拓展）
Higher sales lead firms to increase production; therefore, unexpected increases in the price level cause higher output, making SRAS upward sloping.
销售增加促使企业扩大生产，因此，意外的物价上升会带来更高的产出，使 SRAS 曲线呈向上倾斜。

本页小结（Summary）
Because wages and many prices adjust only slowly—due to annual reviews and menu costs—unexpected price changes alter firms’ real costs and demand conditions, raising or lowering output along an upward-sloping SRAS curve.
由于工资和许多价格只会缓慢调整（年度调薪、菜单成本等），意外的物价变化会改变企业的实际成本和需求状况，使产出沿着向上倾斜的 SRAS 曲线升降。

Slide 17 — Shifts of SRAS versus Movements along It （第17页——短期总供给曲线的平移与沿曲线移动）

Knowledge Points (知识点)

SRAS and the short-run price–quantity relationship（SRAS 与短期价格-产出关系）
Movement along SRAS vs. shift of SRAS（沿 SRAS 移动与 SRAS 平移的区别）
Effects of labor force and capital stock on SRAS（劳动力与资本存量变化对 SRAS 的影响）

🔹Knowledge Point 1 — SRAS as a Short-run Relationship（SRAS 作为短期关系）

Explanation（解释）
The short-run aggregate supply curve shows the short-run relationship between the price level and the quantity of goods and services firms are willing to supply, holding constant all other variables that affect the willingness of firms to supply.
在其他影响企业供给意愿的变量保持不变时，短期总供给曲线描述的是物价水平与企业愿意提供的商品和服务数量之间的短期关系。

Example（例子）
Given current technology, capital stock, labor force, and input prices, a higher price level leads firms to supply more output along the existing SRAS curve.
在既定技术、资本存量、劳动力和投入价格不变的前提下，更高的物价水平会使企业沿既有 SRAS 曲线提供更多产出。

Extension（拓展）
SRAS is drawn conditional on these “other things equal” assumptions; relaxing them—such as changing capital or labor—shifts SRAS rather than moving along it.
SRAS 是在“其他条件不变”的假设下绘制的，一旦这些条件本身发生变化（如资本或劳动力改变），就会引起 SRAS 的平移，而不是沿曲线移动。

🔹Knowledge Point 2 — Movements along vs. Shifts of SRAS（沿曲线移动与曲线平移）

Explanation（解释）
If the price level changes but other variables are unchanged, the economy moves up or down along a stationary SRAS curve—this is a movement along SRAS.
当物价水平变化而其他变量不变时，经济会在既定 SRAS 曲线上下移动，这叫“沿 SRAS 曲线移动”。

If any variable other than the price level changes and affects firms’ willingness to supply, the entire SRAS curve shifts.
如果在物价水平不变的情况下，其他任何变量改变了企业的供给意愿，则整条 SRAS 曲线会平移。

Example（例子）
A temporary oil price shock that raises input costs shifts SRAS left at all price levels; by contrast, a one-time increase in the price level with no change in costs causes a move up along the existing SRAS.
一次性油价冲击提高投入成本，会在所有物价水平下减少供给，使 SRAS 整体左移；相反，如果只是物价水平上升而成本不变，则只是沿原有 SRAS 向上移动。

Extension（拓展）
Correctly distinguishing between movements and shifts is essential for interpreting macroeconomic diagrams and understanding whether changes are driven by costs/productivity or by demand-side factors.
正确区分“沿曲线移动”与“曲线平移”，对于理解宏观图形、判断变化是由成本和生产率还是由需求因素驱动至关重要。

🔹Knowledge Point 3 — Labor Force, Capital Stock, and SRAS Shifts（劳动力与资本存量对 SRAS 的影响）

Explanation（解释）
A firm will supply more output at every price level if it has more workers and more physical capital. The same is true for the economy as a whole: as the labor force and capital stock grow, firms can supply more output at every price level, shifting SRAS to the right.
如果企业拥有更多劳动者和物质资本，它在任何物价水平下都能提供更多产出。对整个经济也是如此：随着劳动力和资本存量增加，企业在每个价格水平下都能提供更多产出，使 SRAS 曲线右移。

If the labor force shrinks, SRAS shifts to the left.
如果劳动力规模下降，SRAS 曲线就会左移。

Example（例子）
In Japan, population aging has led to a declining labor force; holding other variables constant, this decrease in the labor force causes Japan’s SRAS curve to shift to the left.
例如，日本人口老龄化导致劳动力减少，在其他条件不变的情况下，这会使日本的 SRAS 曲线左移。

Extension（拓展）
Similarly, large waves of immigration, increased labor-force participation, or major capital investment programs can shift SRAS to the right by increasing productive capacity in the short to medium run.
同样，大规模移民、劳动参与率上升或重大资本投资计划也会通过提高短中期生产能力，使 SRAS 向右平移。

Image/Data Analysis（图像或数据分析）
在教材图中，SRAS 右移表现为在相同的物价水平下，新的曲线对应更高的实际 GDP；左移则是在相同物价水平下，对应的实际 GDP 更低。以日本为例，因劳动力减少，短期总供给曲线整体向左移动，潜在产出和短期均衡产出都随之下降。

本页小结（Summary）】
短期总供给曲线在“其他条件不变”下刻画价格与产出的关系：物价变化只会导致沿 SRAS 曲线移动，而劳动力、资本等供给因素的变化会使 SRAS 整体平移；劳动力和资本增加使 SRAS 右移，减少则使其左移。

Slide 18 — Technology & Expected Future Price Level （第18页——技术进步与未来物价预期）

Knowledge Points (知识点)

Technological change and productivity（技术进步与生产率）
Effect of technological change on SRAS（技术进步对 SRAS 的影响）
Expected changes in the future price level and SRAS（未来物价预期变化对 SRAS 的影响）

🔹Knowledge Point 1 — Technological Change and Productivity（技术进步与生产率）

Explanation（解释）
As positive technological change takes place, the productivity of workers and machinery increases: firms can produce more goods and services with the same amount of labor and capital.
随着积极的技术变革发生，劳动者和机器设备的生产率提高，企业可以用相同数量的劳动与资本生产出更多的商品和服务。

Example（例子）
The introduction of automation software in a factory allows the same number of workers to operate more machines and complete more tasks per hour.
例如，工厂引入自动化软件后，同样数量的工人可以操作更多机器，每小时完成更多任务。

Extension（拓展）
In growth theory, this is often described as an increase in total factor productivity (TFP), which raises output for given inputs and is a key driver of long-run economic growth.
在增长理论中，这通常被描述为全要素生产率（TFP）的上升，在既定投入下提高产出，是长期经济增长的核心动力之一。

🔹Knowledge Point 2 — Technology and SRAS Shifts（技术变革与 SRAS 曲线平移）

Explanation（解释）
Higher productivity reduces firms’ costs of production and allows them to produce more output at every price level. As a result, the short-run aggregate supply curve shifts to the right.
生产率提高会降低企业的单位成本，使其在每一个物价水平下都能提供更多产出，因此短期总供给曲线向右平移。

Example（例子）
When a country upgrades its communication and logistics infrastructure, firms can coordinate production and shipping more efficiently, so the same prices now correspond to higher quantities of real GDP supplied.
当一国升级通信与物流基础设施后，企业能更高效地组织生产和运输，在相同价格水平下提供的实际 GDP 数量增加。

Image/Data Analysis（图像或数据分析）
在总结表中，“productivity” 一行显示：生产率提高使 SRAS 从 SRAS₁ 向右移到 SRAS₂，对应说明是 “costs of producing output fall”（生产成本下降）。
在图像中，右移表现为在同一价格水平下，新的 SRAS₂ 对应更高的实际 GDP。

Extension（拓展）
Technological regress, or negative shocks such as cyberattacks or widespread equipment failures, would do the opposite—raising costs and shifting SRAS left.
相反，如果出现技术退步或大规模设备故障等负面冲击，则会提高成本，使 SRAS 向左移动。

🔹Knowledge Point 3 — Expected Future Price Level and SRAS（未来物价预期与 SRAS）

Explanation（解释）
If workers and firms believe the overall price level will increase by a certain percentage next year, they will try to adjust wages and prices upward by the same percentage today.
如果劳动者和企业相信未来一年总体物价水平将上涨某个百分比，他们会尝试立即把工资和价格按同样比例上调。

These wage and price increases raise production costs at every level of real GDP, shifting the short-run aggregate supply curve to the left.
这种工资和价格上调提高了各个产出水平下的生产成本，从而使短期总供给曲线整体左移。

Example（例子）
If a labor union expects 3% inflation next year, it negotiates a 3% wage increase to preserve purchasing power. Similar adjustments throughout the economy raise costs by about 3%, shifting SRAS left so that any level of real GDP is now associated with a price level about 3% higher.
例如，工会预期明年通胀率为 3%，便谈判 3% 的工资涨幅以维持购买力；经济中其他劳动者和企业作出类似调整后，整体成本约上升 3%，SRAS 左移，使任何给定的实际 GDP 水平都对应更高的物价。

Image/Data Analysis（图像或数据分析）
在图 23.3 中，若企业和工人预期 2019 年物价比 2018 年高 3%，SRAS 曲线从 SRAS₂₀₁₈ 向左移到 SRAS₂₀₁₉；图上的同一实际 GDP（20 万亿）点，对应的价格水平从 115 上升到约 118.5。
这说明：未来物价预期越高，当前成本越高，短期总供给越少。

Extension（拓展）
In general, if workers and firms expect the price level to rise (fall) by a given percentage, SRAS shifts left (right) by an equivalent amount, holding all other SRAS determinants constant.
一般而言，在其他条件不变时，若工人和企业预期物价上升（下降）若干百分比，SRAS 就会相应左移（右移）同样的幅度。

本页小结（Summary）
Positive technological change raises productivity and shifts SRAS to the right by lowering costs, whereas higher expected future price levels raise current wages and prices, increasing costs and shifting SRAS to the left.
技术进步通过降低成本使 SRAS 右移，而更高的未来物价预期会推高当前工资与价格、增加成本，使 SRAS 左移。

Slide 19 — Expectations Adjustment & Supply Shocks （第19页——预期修正与供给冲击）

Knowledge Points (知识点)

Adjustments to past errors in price expectations（对过去物价预期误差的修正）
Unexpected changes in natural resource prices（关键自然资源价格的意外变化）
Summary of SRAS shift factors（短期总供给平移因素总结）

🔹Knowledge Point 1 — Adjustments to Past Expectation Errors（对过去预期误差的修正）

Explanation（解释）
Workers and firms sometimes make incorrect predictions about the price level. As time passes, they attempt to compensate for these errors in new wage and price contracts.
劳动者和企业有时会对物价水平作出错误预测，随后会在新的工资与价格合同中纠正这些误差。

If the actual price level turns out higher than they had expected, new contracts will demand higher wages and prices, increasing costs and shifting SRAS to the left; if the price level was lower than expected, contracts will adjust downward and SRAS shifts to the right.
如果实际物价高于原先预期，新合同会要求更高工资和价格，从而提高成本、使 SRAS 左移；若实际物价低于预期，则工资和价格调整得更温和，成本下降、SRAS 右移。

Example（例子）
Delta’s pilots sign a contract with only small wage increases because both sides expect only small increases in the price level. If inflation turns out much higher, the union will demand a bigger wage increase in the next contract; these higher wages raise Delta’s costs and, more broadly, shift SRAS left as similar contracts are renegotiated across the economy.
例如，达美航空与飞行员签订合同时只约定小幅加薪，因为双方都预期物价涨幅不大。若实际通胀远高于预期，工会将在下一轮合同谈判中要求更大幅加薪；更高的工资提高达美的成本，而且如果整个经济中都发生类似调整，就会推动 SRAS 整体左移。

Image/Data Analysis（图像或数据分析）
图中显示：当企业和工人意识到过去低估了物价（实际水平高于预期）时，新合同中的工资与价格上调，SRAS 曲线从较低的 SRAS₂₀₁₈ 向左移至更陡的 SRAS₂₀₁₉；同一实际 GDP（20 万亿）对应更高的价格水平。

Extension（拓展）
This mechanism links the dynamics of inflation expectations to supply-side behavior: persistent underestimation of inflation leads to repeated leftward SRAS shifts as contracts catch up.
这一机制把通胀预期的动态与供给行为联系起来：如果长期低估通胀，后续合同不断“追涨”就会反复推动 SRAS 左移。

🔹Knowledge Point 2 — Supply Shocks from Natural Resource Prices（自然资源价格变动带来的供给冲击）

Explanation（解释）
An unexpected event that causes the SRAS curve to shift is called a supply shock. Supply shocks are often caused by unexpected increases or decreases in the prices of important natural resources.
任何意外事件使短期总供给曲线发生平移，都称为“供给冲击”；它往往来自关键自然资源价格的意外上涨或下跌。

Oil prices are particularly volatile; many firms use oil directly or indirectly in production, so sudden changes in oil prices can substantially change production costs.
石油价格尤其波动剧烈，很多企业在生产中直接或间接使用石油，因此油价的突然变化会大幅改变生产成本。

Example（例子）
If oil prices rise unexpectedly, firms that use oil (or oil-based inputs such as plastics) face higher costs. Gasoline prices rise, increasing transportation costs; utilities that burn oil face higher electricity costs. To supply the same level of output, firms must receive higher prices, so SRAS shifts to the left.
例如，如果油价意外大涨，使用石油或塑料等石油制品的企业会面临更高成本；汽油价格上涨增加运输费用，烧油发电的公用事业电价也会上升。要维持同样的产出水平，企业必须获得更高销售价格，因此 SRAS 曲线左移。

Extension（拓展）
Conversely, a sharp fall in oil prices or other key input prices is a positive supply shock: costs fall, firms can supply more at every price level, and SRAS shifts to the right.
相反，油价或其他关键投入价格的大幅下降就是正向供给冲击：成本下降，企业在各个价格水平下都能提供更多产出，SRAS 右移。

🔹Knowledge Point 3 — Summary Table of SRAS Shift Factors（短期总供给平移因素总结）

Explanation（解释）
The summary table lists major variables and how their increases affect SRAS:

Increase in labor force or capital stock → SRAS shifts right (more output can be produced at every price level);
Increase in productivity → SRAS shifts right (lower production costs);
Increase in the expected future price level → SRAS shifts left (workers and firms raise wages and prices);
Workers and firms adjusting to previously underestimated prices → SRAS shifts left;
Increase in the expected price of an important natural resource → SRAS shifts left (higher input costs).
总结表列出了主要变量及其变化对 SRAS 的影响：
劳动力或资本存量增加 → SRAS 右移（每个价格水平能生产更多产出）；
生产率提高 → SRAS 右移（生产成本下降）；
预期未来物价水平上升 → SRAS 左移（工人和企业提高工资与价格）；
对过去低估物价的修正 → SRAS 左移；
预期重要自然资源价格上升 → SRAS 左移（投入成本上升）。

Image/Data Analysis（图像或数据分析）
在表格中，每一行都配有示意图：

右移情形（劳动力/资本、生产率）：SRAS₁ 在左，SRAS₂ 在右；
左移情形（未来物价预期、调整错误、自然资源价格上升）：SRAS₂ 在左，SRAS₁ 在右。
所有图像都以“Price level”为纵轴、“Real GDP”为横轴，红色曲线向右或向左平行移动，直观展示各因素对 SRAS 的影响方向。

Extension（拓展）
记忆技巧：凡是“降低成本或增加可生产能力”的因素（劳动、资本、技术、负向资源价格变化）→ SRAS 右移；凡是“提高单位成本”的因素（更高的预期物价、修正预期、资源价格上涨）→ SRAS 左移。
一个简单口诀是：“增能降本右，涨价提成本左。”

本页小结（Summary）
When workers and firms revise their expectations or natural resource prices change unexpectedly, production costs shift and SRAS moves left or right; together with labor, capital, and technology changes, these factors fully explain the main causes of SRAS shifts.
当劳动者与企业修正物价预期或关键自然资源价格发生意外波动时，生产成本会改变，从而使 SRAS 左移或右移；再结合劳动力、资本与技术变化，这些因素基本解释了短期总供给曲线平移的主要原因。

Slide 20 — Macroeconomic Equilibrium in the Long Run and the Short Run （第20页——长期与短期的宏观经济均衡）

Knowledge Points (知识点)

Definition of macroeconomic equilibrium with AD, SRAS, and LRAS（AD、SRAS 与 LRAS 共同决定的宏观经济均衡）
Long-run equilibrium at potential GDP（潜在 GDP 上的长期均衡）
Interpretation of the equilibrium graph（均衡图形的含义与信息）

🔹Knowledge Point 1 — AD–SRAS–LRAS Macroeconomic Equilibrium（AD–SRAS–LRAS 的宏观经济均衡）

Explanation（解释）
Macroeconomic equilibrium occurs where the aggregate demand curve (AD) intersects the short-run aggregate supply curve (SRAS); in the extended model, we also show the long-run aggregate supply curve (LRAS) on the same graph.
宏观经济均衡出现在总需求曲线（AD）与短期总供给曲线（SRAS）的交点；在扩展模型中，我们还在同一张图上加入长期总供给曲线（LRAS）。

In Figure 23.4, equilibrium is at a real GDP of 20.0 trillion dollars and a price level of about 115.
在图 23.4 中，均衡点对应的实际 GDP 为 20 万亿美元，价格水平约为 115。

Example（例子）
If households, firms, government, and the foreign sector plan to buy exactly 20 trillion dollars of output at the price level of 115, and firms are willing to supply exactly 20 trillion at that price, the economy is in macroeconomic equilibrium.
如果家庭、企业、政府和国外部门在物价 115 时计划购买恰好 20 万亿美元的产出，而企业也愿意在该价格下提供恰好 20 万亿的产出，经济就处于宏观均衡。

Extension（拓展）
The AD–SRAS–LRAS framework allows us to analyze not only the current equilibrium but also how shocks or policy changes move the economy away from or back to potential GDP.
AD–SRAS–LRAS 框架不仅能描述当前均衡，还能分析外生冲击或政策变化如何使经济偏离或回到潜在 GDP。

Image/Data Analysis（图像或数据分析）
图中：向右上倾斜的是 SRAS，向右下倾斜的是 AD，垂直线是 LRAS。
三条曲线在同一点相交，横轴为 Real GDP（2012 年美元，万亿），纵轴为 Price level（GDP 平减指数）。交点显示，在价格水平 115 时，实际 GDP 为 20.0，AD 与 SRAS 的计划支出和供给刚好相等。

🔹Knowledge Point 2 — Long-run Equilibrium at Potential GDP（潜在 GDP 上的长期均衡）

Explanation（解释）
When the AD and SRAS curves intersect at a point on the LRAS curve, the economy is in long-run macroeconomic equilibrium and operating at potential GDP.
当 AD 与 SRAS 的交点刚好落在 LRAS 上时，经济处于长期宏观均衡，运行在潜在 GDP 水平。

At potential GDP, firms operate at their normal capacity, and everyone who wants a job can find one, except for structural and frictional unemployment.
在潜在 GDP 下，企业以正常产能生产，除结构性与摩擦性失业外，愿意工作的人都能就业。

Example（例子）
If LRAS is vertical at 20 trillion dollars, and AD 与 SRAS 的交点也在 20 万亿美元处，则表明经济既在短期均衡，又在长期均衡，没有周期性失业。
如果 LRAS 垂直于 20 万亿的位置，而 AD 与 SRAS 的交点也落在 20 万亿处，就说明经济既处于短期均衡，又处于长期均衡，几乎不存在周期性失业。

Extension（拓展）
Even when the economy is in long-run equilibrium at a point in time, future shocks to AD or SRAS can move the economy away from potential GDP, leading to recessions or expansions.
即使某一时点经济在潜在产出上实现长期均衡，未来的 AD 或 SRAS 冲击仍可能使经济偏离潜在 GDP，产生衰退或扩张。

🔹Knowledge Point 3 — Why the Economy Is Often Not in Long-run Equilibrium（为何现实中常常偏离长期均衡）

Explanation（解释）
The text emphasizes that the economy is often not in long-run macroeconomic equilibrium, because various forces—changes in spending, expectations, technology, or resource prices—constantly disturb AD or SRAS.
教材指出，现实中经济往往不处于长期均衡，因为支出、预期、技术或资源价格的各种变化不断冲击 AD 或 SRAS。

Example（例子）
An unexpected rise in interest rates reducing investment, or an oil price shock raising production costs, can quickly push the economy away from the LRAS intersection point.
例如，利率意外上升导致投资下降，或油价冲击提高生产成本，都能迅速将经济从 LRAS 交点拉开。

Extension（拓展）
Subsequent sections analyze how these forces create recessions, expansions, and supply shocks, and how wages and prices adjust over time to restore long-run equilibrium.
后续内容会分析这些力量如何造成衰退、扩张和供给冲击，以及工资和价格如何逐步调整使经济重新回到长期均衡。

本页小结（Summary）
Macroeconomic equilibrium occurs where AD and SRAS intersect; when this point also lies on LRAS, the economy is at potential GDP, but real economies are continually pushed away from and back toward this long-run equilibrium by various shocks.
宏观经济均衡由 AD 与 SRAS 的交点决定；当该点位于 LRAS 上时，经济处于潜在 GDP 水平，但现实经济会在各种冲击作用下不断偏离和回归这一长期均衡。

Slide 21 — Recession and Long-run Adjustment Back to Potential GDP （第21页——衰退与回归潜在 GDP 的长期调整）

Knowledge Points (知识点)

Short-run effect of a decline in aggregate demand（总需求下降的短期效应：衰退）
Long-run adjustment of wages and SRAS（工资调整与 SRAS 的长期修正）
Graphical path from point A → B → C（从 A 点到 B 点再到 C 点的图像路径）

🔹Knowledge Point 1 — Short-run Recession from Falling AD（AD 下降导致的短期衰退）

Explanation（解释）
To simplify the analysis, we assume initially no inflation (price level = 115) and no long-run growth (potential GDP = 20.0 trillion).
为简化分析，教材假设起初不存在通胀（价格水平为 115），也没有长期增长（潜在 GDP 为 20 万亿）。

Suppose rising interest rates cause firms to cut spending on factories and equipment and households to reduce new-home purchases. This decline in investment shifts the AD curve leftward from AD1 to AD2.
假设利率上升使企业减少在厂房设备上的支出、家庭减少购房投资，这一投资下降会使 AD 曲线从 AD1 向左移到 AD2。

In the new short-run equilibrium, real GDP falls from 20.0 to about 19.8 trillion dollars and is below potential GDP—this is a recession.
在新的短期均衡中，实际 GDP 从 20 万亿降至约 19.8 万亿，低于潜在 GDP，经济进入衰退。

Example（例子）
Text describes this as the move from point A (initial long-run equilibrium) to point B, where AD2 intersects the original SRAS1 at a lower price level (115 → 113) and lower output.
教材将这一过程描述为：均衡从点 A（原始长期均衡）移动到点 B，在 B 点 AD2 与原来的 SRAS1 相交，价格从 115 降到 113，产出下降。

Extension（拓展）
At point B, firms experience declining profits and respond with layoffs; unemployment rises above the natural rate, indicating cyclical unemployment.
在 B 点，企业利润下滑，不得不裁员，失业率高于自然失业率，体现了周期性失业。

Image/Data Analysis（图像或数据分析）
图 23.5 的第一步：AD 从 AD1 左移到 AD2，均衡从 A 点落到 B 点；横轴从 20.0 减到 19.8，纵轴的价格水平从 115 降到 113。LRAS 仍垂直于 20.0 处，显示潜在产出没有改变。

🔹Knowledge Point 2 — Long-run Adjustment of Wages and SRAS（工资与 SRAS 的长期调整）

Explanation（解释）
We know recessions eventually end because there are forces that push the economy back to potential GDP in the long run.
我们知道衰退不会永久持续，因为有力量在长期内推动经济回归潜在 GDP。

At point B, the price level is lower than workers and firms had expected. Over time, they adjust to this lower price level: workers accept lower nominal wages (each dollar of wage buys more goods), and firms are more willing to accept lower prices for their products.
在 B 点，实际物价低于工人和企业原先的预期。随着时间推移，工人会逐渐接受较低的名义工资（因为每一美元工资可以买到更多商品），企业也更愿意接受较低的产品价格。

These reductions in wages and other costs shift the SRAS curve to the right, from SRAS1 to SRAS2.
工资与其他成本的下降会使 SRAS 曲线从 SRAS1 向右移到 SRAS2。

Example（例子）
High unemployment during the recession weakens workers’ bargaining power, making them more willing to accept lower wages; lower wage costs encourage firms to expand production at any given price level.
衰退期间高失业率削弱工人的谈判能力，使其更愿意接受降薪；较低的工资成本则鼓励企业在任何既定价格水平下扩大产出。

Extension（拓展）
This mechanism illustrates how the labor market and price adjustments restore long-run equilibrium without active policy intervention, consistent with the classical long-run view.
这一机制说明，在没有积极政策干预的情况下，劳动力市场和价格的调整如何自发地恢复长期均衡，体现了古典经济学的长期视角。

Image/Data Analysis（图像或数据分析）
图 23.5 的第二步和第三步：

第一步：从 A 到 B（AD1 → AD2）；
第二步：随着工资和成本下降，SRAS 从 SRAS1 右移到 SRAS2，均衡从 B 沿 AD2 移到 C。
在 C 点，实际 GDP 回到 20.0 万亿（与 LRAS 相交），但价格水平继续下降到约 111，表明长期内经济在更低的物价水平下恢复到潜在产出。

🔹Knowledge Point 3 — Path A → B → C: From Long-run Equilibrium to Recession and Back（A→B→C：从长期均衡到衰退再回归）

Explanation（解释）
The full story combines demand and supply adjustments:

Initial long-run equilibrium at A (AD1, SRAS1, LRAS all intersect);
Negative demand shock moves economy to B (AD2 with SRAS1);
Cost and wage adjustments shift SRAS to SRAS2 and move equilibrium to C on LRAS.
完整过程结合了需求与供给的调整：
1）起点 A：AD1、SRAS1 与 LRAS 在潜在产出上相交；
2）负向需求冲击将经济推到 B 点（AD2 与 SRAS1 相交）；
3）成本与工资下调，使 SRAS 右移到 SRAS2，均衡沿 AD2 移动到 C 点并重新落在 LRAS 上。

Example（例子）
Think of a housing-market bust: investment in new homes collapses (AD 下降)，经济进入衰退（A→B）；几年后，工资和租金下调，企业成本降低，产出恢复到潜在水平，但房价和物价总水平比最初更低（B→C）。
可以把它类比为房地产泡沫破裂：新房投资崩溃（AD 下降），经济衰退（A→B）；几年后，工资和房租下降，企业成本降低，产出恢复到潜在水平，但房价与总体物价低于最初（B→C）。

Extension（拓展）
This adjustment process highlights a trade-off for policymakers: without intervention, the economy can self-correct but may endure a prolonged period of high unemployment; with active stabilization policy, governments try to speed up the move from B to C.
这一调整过程也凸显了政策权衡：若不干预，经济终会自我修复，却可能经历长期高失业；若实施稳定政策，政府试图加快从 B 到 C 的过渡。

本页小结（Summary）
A negative demand shock shifts AD left and moves the economy from full-employment equilibrium to a recessionary short-run equilibrium; over time, falling wages and prices shift SRAS right, bringing real GDP back to potential while leaving the price level permanently lower.
当负向需求冲击使 AD 左移时，经济会从充分就业的长期均衡跌入衰退性的短期均衡；随着工资与价格逐步下降，SRAS 右移，实际 GDP 回到潜在水平，而价格水平则永久性地低于原先水平。

Slide 22 — Automatic Adjustment and Policy Choices （第22页——自动调节机制与政策选择）

Knowledge Points (知识点)

Key conclusion of a negative AD shock（总需求下降的关键结论）
Automatic mechanism back to potential GDP（回到潜在 GDP 的自动调节机制）
Policy alternative and economists’ debate（政策替代方案与经济学家的争论）

🔹Knowledge Point 1 — Long-run Effect of a Decline in Aggregate Demand（总需求下降的长期影响）

Explanation（解释）
In the short run, a fall in aggregate demand causes a recession: real GDP is below potential and unemployment rises.
在短期内，总需求下降会引发衰退：实际 GDP 低于潜在水平，就业不足、失业率上升。

In the long run, however, falling wages and prices shift SRAS to the right so that output returns to potential GDP; only the price level ends up lower.
但在长期中，工资与价格下降会推动 SRAS 向右移动，使产出回到潜在 GDP，最终只留下更低的价格水平这一结果。

Example（例子）
In the AD1→AD2 recession example, GDP falls from 20.0 to 19.8 trillion in the short run but later returns to 20.0 trillion, while the price level drops from 115 to about 111.
在 AD1→AD2 的例子中，短期内 GDP 从 20 万亿降到 19.8 万亿，但随后又回到 20 万亿，同时价格水平从 115 降到约 111。

Extension（拓展）
This illustrates that AD shocks have permanent effects on the price level but not on long-run real GDP, consistent with the idea that potential GDP is determined by supply-side factors.
这说明 AD 冲击会对价格水平产生持久影响，但不会改变长期的实际 GDP，与“潜在 GDP 由供给侧因素决定”的观点一致。

🔹Knowledge Point 2 — The Automatic Mechanism（自动调节机制）

Explanation（解释）
Economists call the process of moving back to potential GDP without government action the “automatic mechanism.”
经济学家把在没有政府政策干预的情况下，经济自动回到潜在 GDP 的过程称为“自动调节机制”。

It works through gradual wage and price adjustments that change SRAS, not AD.
该机制通过工资和价格的渐进调整来改变 SRAS，而不是改变 AD。

Example（例子）
During a recession, high unemployment puts downward pressure on wages; as wages fall, firms’ costs decline, SRAS shifts right, and output recovers.
在衰退期，高失业率压低工资；随着工资下降，企业成本降低，SRAS 向右移动，产出逐步恢复。

Extension（拓展）
The slides note that this adjustment from SRAS1 to SRAS2 does not happen instantly and may take several years, which explains why recessions can be long-lasting even if they eventually end.
课件指出，从 SRAS1 调整到 SRAS2 不是瞬间完成，可能需要数年时间，这解释了为何衰退可以持续很久，即便最终会结束。

🔹Knowledge Point 3 — Policy Alternative and Debate（政策替代方案与争论）

Explanation（解释）
Instead of waiting for the automatic mechanism, governments can use monetary or fiscal policy to shift AD right and close the recessionary gap more quickly.
与其等待自动机制发挥作用，政府可以通过货币政策或财政政策向右推动 AD，更快地弥合衰退缺口。

Economists debate whether it is better to rely on the automatic mechanism or to actively stabilize the economy with policy.
经济学家就“应依赖自动调节，还是应通过政策主动稳定经济”存在争论。

Example（例子）
Keynesian economists generally favor active stabilization policies, while more classical or new classical economists stress the costs and lags of policy and are more willing to rely on self-correction.
凯恩斯学派通常主张积极的稳定政策，而古典与新古典经济学家更强调政策的滞后与成本，更愿意依赖经济的自我修复。

Extension（拓展）
This debate underlies real-world policy choices: for example, whether to respond to a downturn with stimulus spending and interest-rate cuts, or to allow markets to adjust over time.
这种争论直接影响现实中的政策选择：面对经济下滑时，是通过刺激支出和降息迅速干预，还是让市场自行调整。

本页小结（Summary）
A negative AD shock creates a short-run recession but, through an automatic mechanism of wage and price adjustment, restores output to potential in the long run—leaving only a lower price level and raising the question of whether governments should accelerate this process with policy.
一次负向 AD 冲击会在短期内造成衰退，但通过工资与价格的自动调整机制，长期中产出会回到潜在水平，只留下较低的物价，同时引发“政府是否应通过政策加快这一过程”的政策争论。

Slide 23 — Expansion and Long-run Adjustment Back to Potential GDP （第23页——扩张与回归潜在 GDP 的长期调整）

Knowledge Points (知识点)

Short-run expansion from an increase in AD（总需求增加导致的短期扩张）
Long-run adjustment when real GDP is above potential（产出高于潜在时的长期调整）
Path A → B → C under positive demand shock（正向需求冲击下的 A→B→C 路径）

🔹Knowledge Point 1 — Short-run Effect of an Increase in AD（总需求增加的短期效应）

Explanation（解释）
If firms become optimistic about the future profitability of investment, investment spending rises and shifts the AD curve to the right from AD1 to AD2.
如果企业对未来投资盈利前景更加乐观，投资支出增加，使 AD 曲线从 AD1 向右移动到 AD2。

The new short-run equilibrium moves from point A to point B: real GDP increases from 20.0 to about 20.3 trillion dollars, and the price level rises from 115 to 118.
新的短期均衡从 A 点移动到 B 点：实际 GDP 从 20 万亿升至约 20.3 万亿，价格水平从 115 升至 118。

Example（例子）
The slides mention the investment booms in information technology and telecommunications in the late 1990s as an example of such optimism-driven expansions.
课件以 20 世纪 90 年代末的信息技术和通信行业投资繁荣为例，说明这种乐观预期驱动的扩张。

Extension（拓展）
At point B, real GDP exceeds potential GDP, so firms operate beyond normal capacity, and some workers who would normally be unemployed or outside the labor force become employed.
在 B 点，实际 GDP 高于潜在 GDP，企业超负荷运转，一些原本结构性或摩擦性失业者、甚至不在劳动力大军中的人也被雇佣。

Image/Data Analysis（图像或数据分析）
图 23.6 中，AD 从 AD1 向右移到 AD2，均衡从 A 点跳到 B 点：横轴从 20.0 增到 20.3，纵轴价格水平从 115 升到 118。B 点处的产出高于垂直的 LRAS（潜在 GDP）。

🔹Knowledge Point 2 — Long-run Adjustment from Expansion（扩张后的长期调整）

Explanation（解释）
Just as an automatic mechanism brings the economy back to potential GDP from a recession, another automatic mechanism brings it back from an above-potential expansion.
类似于从衰退回归潜在 GDP 的自动机制，经济也会从“超额扩张”的状态自动回到潜在产出。

Because the price level is now higher than expected, workers and firms adjust: workers demand higher nominal wages and firms raise prices, increasing production costs.
由于价格水平高于之前的预期，工人和企业会进行调整：工人要求更高的名义工资，企业提高产品价格，生产成本上升。

These higher costs shift the SRAS curve leftward from SRAS1 to SRAS2, reducing output back to potential GDP.
成本上升会使 SRAS 曲线从 SRAS1 向左移动到 SRAS2，从而把产出压回潜在 GDP。

Example（例子）
Low unemployment during the boom strengthens workers’ bargaining power, making it easier for unions and employees to negotiate wage increases that push SRAS left.
扩张期失业率很低，工人议价能力更强，更容易谈成加薪合同，从而推动 SRAS 向左移动。

Extension（拓展）
In the new long-run equilibrium at point C, real GDP returns to 20.0 trillion, but the price level stays higher (around 121), showing that positive demand shocks permanently raise the price level.
在新的长期均衡 C 点，实际 GDP 回到 20 万亿，但价格水平维持在更高的约 121，说明正向需求冲击会永久性地抬高物价水平。

Image/Data Analysis（图像或数据分析）
图 23.6 中的路径：

第一步：AD1→AD2，均衡 A→B（GDP 高于潜在，物价 115→118）；
第二步：SRAS1→SRAS2，均衡 B 沿 AD2 移到 C 点（GDP 回到 20.0，但物价升至约 121）。

🔹Knowledge Point 3 — Comparing Negative and Positive AD Shocks（正负需求冲击的对比）

Explanation（解释）
Both negative and positive AD shocks change real GDP in the short run but leave long-run output at potential; in both cases, the long-run effect is a different price level.
无论是负向还是正向的 AD 冲击，短期内都会改变实际 GDP，但长期中产出都会回到潜在水平；两种情况下长期影响都是不同的价格水平。

Example（例子）
Negative shock：AD1→AD2（左移），长期价格水平下降；
Positive shock：AD1→AD2（右移），长期价格水平上升。
负向冲击：AD1→AD2（向左），长期物价下降；
正向冲击：AD1→AD2（向右），长期物价上升。

Extension（拓展）
This symmetry helps explain why central banks focus on stabilizing aggregate demand: large swings in AD mainly show up as inflation or deflation in the long run, even if real GDP returns to potential.
这种对称性解释了为何央行要致力于稳定总需求：即便实际 GDP 终究会回到潜在水平，AD 的大幅波动在长期主要会表现为通胀或通缩。

本页小结（Summary）
A positive demand shock temporarily pushes real GDP above potential and raises the price level, but as wages and prices adjust upward, SRAS shifts left, bringing output back to potential while leaving the economy with permanently higher prices.
正向需求冲击会暂时把实际 GDP 推高到潜在水平之上并抬高物价，但随着工资和价格上调，SRAS 向左移动，产出回到潜在水平，只留下更高的长期价格水平。

Slide 24 — Supply Shocks and Stagflation （第24页——供给冲击与滞涨）

Knowledge Points (知识点)

Definition and source of supply shocks（供给冲击的含义与来源）
Short-run effect of an adverse supply shock（不利供给冲击的短期效应）
Stagflation: rising prices with falling output（滞涨：高通胀与低增长并存）

🔹Knowledge Point 1 — What Is a Supply Shock?（什么是供给冲击）

Explanation（解释）
A supply shock is an unexpected event that causes the short-run aggregate supply (SRAS) curve to shift, usually by suddenly changing firms’ production costs.
供给冲击是指意外事件导致短期总供给曲线（SRAS）移动，通常是通过突然改变企业的生产成本实现的。

Adverse supply shocks often come from sharp increases in the prices of important natural resources like oil.
不利供给冲击往往来源于石油等重要自然资源价格的大幅上涨。

Example（例子）
If oil prices rise substantially, any firm that uses oil directly or indirectly (through plastics, transportation, or electricity) faces higher costs.
当油价大幅上涨时，直接使用石油或通过塑料、运输、电力等间接使用石油的企业成本都会上升。

Extension（拓展）
Because these resources are widely used, a single shock can affect many industries at once, making supply shocks economy-wide rather than sector-specific.
由于这些资源应用极为广泛，一次价格冲击可以同时影响众多行业，使供给冲击具有“全经济性”而非个别行业性。

🔹Knowledge Point 2 — Short-run Effect of an Adverse Supply Shock（不利供给冲击的短期效应）

Explanation（解释）
When costs rise unexpectedly, firms will only supply the same level of output if they receive higher prices; SRAS therefore shifts left from SRAS1 to SRAS2.
当成本意外上升时，企业只有在获得更高价格时才愿意提供原来的产量，因此 SRAS 会从 SRAS1 向左移动到 SRAS2。

In the new short-run equilibrium, the price level is higher but real GDP is lower.
新的短期均衡中，价格水平更高，而实际 GDP 更低。

Example（例子）
The slide’s numerical example shows the price level rising from 115 to 117 while real GDP falls from 20.0 to 19.7 trillion dollars.
课件中的数字示例显示：价格水平从 115 上升到 117，而实际 GDP 从 20 万亿降至 19.7 万亿。

Extension（拓展）
Unlike a demand shock, an adverse supply shock worsens both inflation and output simultaneously, creating a difficult trade-off for policymakers.
与需求冲击不同，不利供给冲击会同时恶化通胀和产出，为政策制定者带来棘手的取舍问题。

Image/Data Analysis（图像或数据分析）
图 23.7(a) 中，AD 不变，SRAS 从 SRAS1 左移到 SRAS2：

交点从 A 移到 B；
横轴 GDP 从 20.0 降到 19.7；
纵轴价格水平从 115 升至 117。

🔹Knowledge Point 3 — Stagflation and Policy Challenges（滞涨与政策难题）

Explanation（解释）
The combination of higher inflation and lower real GDP caused by an adverse supply shock is called “stagflation” (stagnation + inflation).
由于不利供给冲击导致通胀上升、产出下降的组合，被称为“滞涨”（经济停滞 + 通货膨胀）。

Example（例子）
Historical episodes like the 1970s oil crises produced stagflation in many advanced economies: prices rose rapidly while unemployment remained high.
历史上的 20 世纪 70 年代石油危机就引发了许多发达国家的滞涨：物价飞涨，而失业率居高不下。

Extension（拓展）
Standard demand-management tools face a dilemma: policies that fight inflation by reducing AD may deepen the recession, while policies that fight recession by boosting AD may worsen inflation.
传统的需求管理工具在此面临两难：抑制 AD 以控制通胀会加深衰退，而刺激 AD 以对抗衰退又会进一步推高通胀。

本页小结（Summary）
Adverse supply shocks such as sharp increases in oil prices shift SRAS left, leading to higher prices and lower real GDP—stagflation—which is harder to treat with standard demand-side policies than simple demand shocks.
石油等关键资源价格的剧烈上升会使 SRAS 向左移动，导致物价上升而实际 GDP 下降，即“滞涨”，这种供给冲击比单纯的需求冲击更难通过传统需求管理政策加以应对。

Slide 25 — Adjustment Back to Potential GDP in the Long Run （第25页——长期回归潜在GDP的调整机制）

Knowledge Points (知识点)

Long-run adjustment after a negative supply shock（负向供给冲击后的长期调整过程）
Wage and price flexibility versus policy intervention（工资与价格调整与政策干预的比较）

🔹Knowledge Point 1 — Long-run Adjustment after a Negative Supply Shock（负向供给冲击后的长期调整过程）

Explanation（解释）
A negative supply shock (such as a sudden oil price increase) shifts the short-run aggregate supply curve left from SRAS₁ to SRAS₂, causing higher prices and lower real GDP in the short run.
负向供给冲击（例如油价突然上涨）会使短期总供给曲线从 SRAS₁ 左移到 SRAS₂，在短期内导致物价上升、实际GDP下降。

Over time, high unemployment and weak output put downward pressure on nominal wages and other input prices, reducing firms’ costs and shifting SRAS back to its original position.
随着时间推移，高失业率和低产出会给名义工资及其他要素价格带来下行压力，降低企业成本，使 SRAS 曲线逐渐向右移回原来的位置。

In the long run, real GDP returns to potential GDP and the price level falls back to its original level, restoring long-run macroeconomic equilibrium.
从长期看，实际GDP回到潜在GDP水平，物价水平回落到原来的水平，经济重新回到长期宏观均衡。

Example（例子）
If an oil shock initially raises the price level from 115 to 117 and reduces real GDP from 20.0 to 19.7 trillion dollars (point A to B), later wage and price adjustments move the economy back to A, with GDP at 20.0 and the price level at 115.
例如，油价冲击最初使物价水平从115升到117、实际GDP从20.0万亿降到19.7万亿（由点A到点B），之后工资和价格下调，经济又回到点A，GDP恢复到20.0万亿、物价回到115。

Extension（拓展）
This long-run self-correction relies on flexible wages and prices; if contracts or regulations keep wages rigid, the adjustment may be very slow.
这种长期自我修复机制依赖于工资和价格的灵活性；如果合同或监管使工资僵固，调整过程会非常缓慢。

Economists describe this process as an “automatic mechanism” because it occurs without new government policies.
经济学家把这一过程称为“自动调节机制”，因为它可以在没有新政府政策的情况下自然发生。

Image/Data Analysis（图像/数据分析）
In panel (b) of Figure 23.7, the leftward shift from SRAS₁ to SRAS₂ moves equilibrium from A to B, with higher P and lower Y.
在图23.7(b) 中，SRAS₁ 左移到 SRAS₂，使均衡由点A转到点B，价格上升、产出下降。

Later, SRAS₂ shifts right back to SRAS₁, moving equilibrium from B to A at the original price level and potential GDP.
随后，SRAS₂ 再次右移回 SRAS₁，使均衡由点B回到点A，价格与潜在GDP恢复到原有水平。

Summary（小结）
A negative supply shock causes temporary stagflation in the short run, but falling wages and input costs eventually return the economy to potential GDP at the original price level.
负向供给冲击会在短期内造成“滞胀”，但随着工资和成本下降，经济最终会回到原有物价水平下的潜在GDP。

🔹Knowledge Point 2 — Wage and Price Flexibility versus Policy Intervention（工资与价格调整与政策干预的比较）

Explanation（解释）
Instead of waiting for the automatic fall in wages and prices, the government could use expansionary fiscal or monetary policy to shift the AD curve to the right.
政府也可以不等待工资和价格自动下调，而是通过扩张性财政或货币政策将AD曲线右移。

This restores real GDP to potential more quickly but keeps the higher price level permanently.
这种做法可以更快把实际GDP拉回潜在水平，但会上升并永久性地维持较高的物价水平。

Example（例子）
Suppose after a supply shock the economy is at point B (P = 117, Y < potential); if policy shifts AD right, equilibrium may move to a point with Y back at potential but P > 117.
例如，供给冲击后经济处于点B（P=117，Y低于潜在），若通过政策使AD右移，新的均衡可能让Y回到潜在水平，但物价P将高于117。

Extension（拓展）
The choice between waiting for automatic adjustment and using policy reflects a trade-off: faster output recovery versus the cost of higher inflation.
在“等待自动调整”和“采取政策干预”之间的选择，实质上是“更快恢复产出”与“更高通胀成本”之间的权衡。

Economists disagree on which is preferable, depending on how costly they judge unemployment and inflation to be.
经济学家对哪种方式更好并无共识，这取决于他们对失业成本和通胀成本的权重判断。

Image/Data Analysis（图像/数据分析）
In the graph, the automatic mechanism keeps AD fixed and lets SRAS move back, returning to point A with the original price level.
在图中，自动机制假定AD不变，仅让SRAS移回，使经济重新回到点A并恢复原有物价水平。

If policy is used, AD shifts right and the new equilibrium would lie to the right of A on LRAS, at higher P but the same potential Y.
若采用政策干预，AD向右移，新均衡将在LRAS上位于A的右侧，物价更高但产出仍等于潜在GDP。

Summary（小结）
Long-run recovery after a supply shock can rely either on slow wage-price adjustment or faster policy-driven AD shifts, with the key trade-off between inflation and the speed of returning to potential GDP.
供给冲击后的长期复苏可以依靠缓慢的工资价格调整，也可以依靠快速的政策推动AD右移，核心权衡在于通胀水平与回归潜在GDP速度之间。

Slide 26 — A Dynamic Aggregate Demand and Aggregate Supply Model（第26页——动态总需求与总供给模型）

Knowledge Points (知识点)

Limitations of the basic static AD–AS model（静态AD–AS模型的局限性）
Core assumptions of the dynamic AD–AS model（动态AD–AS模型的核心假设）
Typical macroeconomic patterns in the dynamic framework（动态框架下的宏观经济典型特征）

🔹Knowledge Point 1 — Limitations of the Basic Static AD–AS Model（静态AD–AS模型的局限性）

Explanation（解释）
The basic AD–AS model assumes no ongoing inflation and no long-run growth in potential GDP, so it predicts that a leftward shift of AD causes a permanently lower price level.
基础AD–AS模型假定不存在持续的通货膨胀、潜在GDP不增长，因此会预测AD左移后物价长期降低。

Historically, however, most economies experience positive trend growth and persistent inflation rather than falling price levels.
但从历史看，大多数经济体长期呈现正向增长与持续通胀，而不是物价水平长期下降。

Example（例子）
Since the 1950s, U.S. real GDP has grown almost every decade while the GDP deflator has trended upward instead of falling during recessions.
例如，自20世纪50年代以来，美国实际GDP几乎每十年都在增长，GDP平减指数总体上升，而不是在衰退后长期下降。

Extension（拓展）
Because the static model ignores growth and trend inflation, it can be misleading for analyzing modern economies with steadily rising productive capacity and money supply.
由于静态模型忽略了经济增长和趋势性通胀，用它分析具有持续产能提升和货币供给扩张的现代经济会产生误导。

Image/Data Analysis（图像/数据分析）
The slide highlights that the prediction “AD left shift → permanently lower P” has not matched post-1930s data, motivating a more realistic dynamic model.
本页强调“AD左移→物价长期下降”的预测与20世纪30年代之后的实际数据不符，从而引出需要更真实的动态模型。

Summary（小结）
Because the static AD–AS model omits long-run growth and ongoing inflation, its predictions about recessions and price levels often conflict with real-world data.
由于静态AD–AS模型忽视长期增长和持续通胀，其对衰退及物价变化的预测往往与现实不符。

🔹Knowledge Point 2 — Core Assumptions of the Dynamic AD–AS Model（动态AD–AS模型的核心假设）

Explanation（解释）
The dynamic model assumes that potential GDP, represented by LRAS, increases continually as labor, capital, and technology improve.
动态模型假定潜在GDP（由LRAS表示）会随着劳动、资本和技术进步而持续上升。

It also assumes that during most years the AD curve shifts right due to growth in consumption, investment, government purchases, and net exports.
同时假定在多数年份中，总需求曲线AD会因消费、投资、政府购买和净出口的增长而向右移动。

Except in periods when expected inflation is very high, the SRAS curve also shifts right each year as costs per unit decline or rise more slowly than prices.
除非预期通胀率非常高，短期总供给曲线SRAS也会因单位成本下降或成本增速低于物价增速而逐年右移。

Example（例子）
If potential GDP grows about 2% per year and AD grows similarly, both LRAS and AD will shift right by roughly 2%, keeping inflation low.
例如，当潜在GDP每年约增长2%、AD也大致以2%速度增长时，LRAS和AD都会大致右移2%，通胀率会保持在较低水平。

Extension（拓展）
When AD grows faster than LRAS (for example due to aggressive monetary expansion), the dynamic model predicts higher inflation; when AD grows slower, it predicts disinflation or recession.
当AD增速快于LRAS（比如扩张性货币政策过度）时，动态模型预测通胀上升；当AD增速慢于LRAS时，则预测通胀回落甚至出现衰退。

Image/Data Analysis（图像/数据分析）
The learning-objective slide summarizes these assumptions: LRAS shifts right every year, AD usually shifts right, and SRAS shifts right except when inflation expectations rise sharply.
学习目标页概括了以上假设：LRAS每年右移，AD在大多数年份右移，而SRAS除非通胀预期大幅上升，否则也会逐年右移。

Summary（小结）
The dynamic AD–AS model embeds growth and trend inflation by letting LRAS, AD, and usually SRAS all shift right over time.
动态AD–AS模型通过让LRAS、AD以及通常的SRAS随时间整体右移，把经济增长和趋势性通胀纳入分析框架。

🔹Knowledge Point 3 — Typical Macroeconomic Patterns in the Dynamic Framework（动态框架下的宏观经济典型特征）

Explanation（解释）
In a “normal” year, LRAS, SRAS, and AD all shift right by similar percentages, leading to higher real GDP with roughly stable inflation.
在“正常年份”中，LRAS、SRAS和AD大致以相近比例右移，使实际GDP提高而通胀率大致稳定。

Recessions or high-inflation episodes arise when AD or SRAS shifts by a very different amount from LRAS.
当AD或SRAS相对于LRAS发生幅度明显不同的移动时，就会出现衰退或高通胀。

Example（例子）
If AD barely shifts while LRAS and SRAS continue to shift right, real GDP growth slows and inflation falls; if AD shifts much more than LRAS, inflation rises.
例如，当AD几乎不动而LRAS与SRAS继续右移时，实际GDP增速放缓、通胀下降；若AD右移远超LRAS，则通胀上升。

Extension（拓展）
This framework helps central banks choose policies that keep AD growth roughly in line with potential GDP growth, stabilizing inflation.
这一框架帮助央行设计政策，使AD增速与潜在GDP增速大致一致，从而稳定通胀。

Image/Data Analysis（图像/数据分析）
Later slides, such as Figure 23.8, illustrate a case where all three curves shift right and the price level remains at 115 while real GDP rises from 20.0 to 20.4, showing growth without extra inflation.
后续如图23.8展示了一个“LRAS、SRAS、AD都右移”的情形：物价保持在115，而实际GDP从20.0升至20.4，体现了“有增长、无额外通胀”的结果。

Summary（小结）
The dynamic AD–AS model explains typical combinations of growth and inflation by comparing how far LRAS, SRAS, and AD shift in each period.
动态AD–AS模型通过比较LRAS、SRAS与AD在每一时期移动的幅度，来解释增长与通胀的不同组合。

Slide 27 — Dynamic Equilibrium: Growth without Inflation（第27页——动态均衡：有增长而无通胀）

Knowledge Points (知识点)

Sequential shifts of LRAS, SRAS, and AD（LRAS、SRAS 与 AD 的依次移动）
New long-run equilibrium with higher real GDP and unchanged price level（价格不变而实际GDP上升的新长期均衡）
Interpretation and policy implications（经济含义与政策启示）

🔹Knowledge Point 1 — Sequential Shifts of LRAS, SRAS, and AD（LRAS、SRAS 与 AD 的依次移动）

Explanation（解释）
Figure 23.8 begins with the economy at point A, where SRAS₁ and AD₁ intersect on LRAS₁ at a price level of 115 and real GDP of $20.0 trillion.
图23.8中，经济最初位于点A，SRAS₁ 与 AD₁ 在 LRAS₁ 上相交，物价水平为115、实际GDP为20.0万亿美元。

Over time, potential GDP rises, shifting LRAS right from LRAS₁ to LRAS₂ as labor, capital, and technology grow.
随后，潜在GDP上升，劳动力、资本和技术进步使LRAS从LRAS₁右移至LRAS₂。

Because the same forces that shift LRAS also raise short-run productive capacity, SRAS shifts right from SRAS₁ to SRAS₂.
由于推动LRAS右移的因素也会在短期内提高产能，SRAS曲线从SRAS₁右移至SRAS₂。

Finally, rising population, income, investment, and government purchases shift AD from AD₁ to AD₂.
最后，人口与收入增加以及投资和政府购买的增长，使AD从AD₁右移到AD₂。

Example（例子）
In the diagram, LRAS, SRAS, and AD all shift right roughly the same distance, keeping the new intersection point B on LRAS₂.
在图中，LRAS、SRAS及AD三条曲线大致等距右移，使新的交点B落在LRAS₂上。

Extension（拓展）
If any of the three curves moved a different distance—say AD shifted more than LRAS—then point B would have a higher price level, producing inflation.
如果三条曲线中有一条移动幅度不同——例如AD右移幅度大于LRAS——则点B的物价水平会高于115，从而产生通胀。

Image/Data Analysis（图像/数据分析）
The figure marks step 1 (initial equilibrium at A), step 2 (LRAS shift), step 3 (SRAS shift), and step 4 (AD shift), visually separating the dynamic process into clear stages.
图中用1到4四个标签依次标出：1为点A的初始均衡，2为LRAS右移，3为SRAS右移，4为AD右移，将动态过程拆解为清晰的阶段。

Summary（小结）
When LRAS, SRAS, and AD all shift right by similar amounts, the economy moves smoothly from one long-run equilibrium to another with higher output.
当LRAS、SRAS与AD以相近幅度同时右移时，经济会从一个长期均衡平滑过渡到产出更高的另一个长期均衡。

🔹Knowledge Point 2 — Higher Real GDP with an Unchanged Price Level（价格不变而实际GDP上升）

Explanation（解释）
At the new equilibrium B, AD₂ intersects SRAS₂ on LRAS₂ with the price level still at 115 but real GDP increased to $20.4 trillion.
在新的均衡点B，AD₂ 与 SRAS₂ 在 LRAS₂ 上相交，物价水平仍为115，但实际GDP已升至20.4万亿美元。

Because aggregate demand and aggregate supply both increased by the same proportion, there is real growth without additional inflation.
由于总需求与总供给按相同比例增加，经济实现了“有实际增长、无额外通胀”。

Example（例子）
If both LRAS and AD grow at roughly 2% per year, real GDP rises 2% while the price level can remain stable, consistent with the movement from A to B.
例如，当LRAS和AD都以每年约2%的速度增长时，实际GDP提高2%，而物价大致稳定，对应图中从A到B的变化。

Extension（拓展）
This scenario describes what economists call “non-inflationary growth,” which many central banks aim for when setting monetary policy.
这种情形被称为“非通胀性增长”，是许多中央银行设定货币政策时追求的目标。

Image/Data Analysis（图像/数据分析）
On the vertical axis, the price level remains at 115 for both A and B; on the horizontal axis, real GDP increases from 20.0 to 20.4, showing pure real expansion.
在纵轴上，点A与点B的物价水平均为115；在横轴上，实际GDP从20.0增加到20.4，图像清楚地显示出纯粹的实际扩张。

Summary（小结）
When AD and AS expand in step with each other, the economy can enjoy higher real output without higher inflation.
当总需求与总供给同步扩张时，经济可以在不提高通胀的情况下实现更高的实际产出。

🔹Knowledge Point 3 — Interpretation and Policy Implications（经济含义与政策启示）

Explanation（解释）
The dynamic AD–AS model shows that long-run inflation depends on how fast AD grows relative to LRAS; stable inflation requires AD growth ≈ LRAS growth.
动态AD–AS模型表明，长期通胀取决于AD相对于LRAS的增长速度；要保持稳定通胀，需要AD增长大致等于LRAS增长。

Policymakers can use this framework to judge whether current demand-side policies are too expansionary (risking inflation) or too weak (risking recession).
政策制定者可以利用该框架判断当前需求管理政策是否过度扩张（通胀风险）或过于紧缩（衰退风险）。

Example（例子）
If potential GDP is growing at 2% but AD is pushed to grow at 5%, the model predicts rising inflation; if AD grows at only 0%, the model predicts falling inflation and possible output gaps.
例如，当潜在GDP以2%增长而AD被推升到5%时，模型预测通胀上升；若AD几乎不增长，则通胀下降并可能出现产出缺口。

Extension（拓展）
By comparing actual inflation and output growth with the dynamic model’s predictions, central banks can adjust interest rates or other tools to keep the economy near a “path” like A → B.
央行可以将实际的通胀和产出增速与动态模型预测进行比较，并据此调整利率等工具，使经济围绕类似A→B的“理想路径”波动。

Image/Data Analysis（图像/数据分析）
In Figure 23.8, the “parallel” rightward shifts of LRAS, SRAS, and AD visually represent a well-balanced macro path where policy has neither overstimulated nor overly restrained demand.
在图23.8中，LRAS、SRAS与AD几乎平行地向右移动，形象地展示了需求既不过度刺激也不过度压制的“均衡增长”路径。

Summary（小结）
The dynamic AD–AS framework links long-run inflation and growth outcomes to how closely aggregate demand growth tracks the growth of potential GDP.
动态AD–AS框架把长期通胀与增长结果与“总需求增长是否贴合潜在GDP增长”直接联系起来。

Slide 29 — Practice: Shifts of Aggregate Demand（第29页——总需求曲线变动练习）

Knowledge Points (知识点)

Events that cause movements along $A D$ vs. shifts of $A D$ （导致总需求曲线移动/曲线上点移动的事件）
How fiscal, monetary and external factors affect $A D$ （财政、货币与外部因素如何影响总需求）

🔹Knowledge Point 1 — Movements along vs. Shifts of Aggregate Demand（总需求曲线上的移动 vs. 曲线整体移动）

Explanation（解释） A change in the overall price level causes a movement along the $A D$ curve, while any other change in spending components $C, I, G, NX$ shifts the entire $A D$ curve. 整体物价水平的变化只会使经济沿着既有的总需求曲线移动；而只要是影响消费 $C$ 、投资 $I$ 、政府购买 $G$ 、净出口 $NX$ 的其他因素变化，就会使整条总需求曲线发生平移。

Example（例子） a. An increase in the price level → move up along $A D$ → quantity of real GDP demanded falls (no shift). a. 物价水平上升 → 沿既有 $A D$ 曲线向上移动 → 所需求的实际 GDP 数量减少（曲线不移动）。

b. An increase in government purchases $G$ → $A D$ shifts right. b. 政府购买 $G$ 增加 → 总需求曲线整体向右移动。

c. Higher income taxes reduce disposable income and $C$ → $A D$ shifts left. c. 所得税提高使可支配收入和消费 $C$ 减少 → 总需求曲线整体左移。

Extension（拓展） We can summarize: factors that change planned spending at every price (fiscal policy, expectations, foreign conditions) shift $A D$ ; pure price-level changes do not. 可以总结为：凡是能在“每一个物价水平下”改变计划支出的因素（财政政策、预期、国外经济状况等）都会使 $A D$ 平移；单纯的物价水平变化只会改变曲线上点的位置。

Image/Data Analysis（图像或数据分析） On the $P$ – $Y$ graph, an increase in $P$ is shown as a move from one point to another along the same $A D$ ; an increase in $G$ is shown as a new $A D_{2}$ to the right of $A D_{1}$ . 在价格水平–实际产出图中，物价上升表现为沿着同一条 $A D$ 曲线从一点移动到另一点；而政府购买增加则表现为从 $A D_{1}$ 向右平移到新的 $A D_{2}$ 。

🔹Knowledge Point 2 — Monetary and External Factors on $A D$ （货币与外部因素对总需求的影响）

Explanation（解释） Interest rates and international conditions mainly affect investment $I$ and net exports $NX$ , thus shifting $A D$ . 利率和国际经济状况主要通过影响投资 $I$ 与净出口 $NX$ 来推动总需求曲线的平移。

Example（例子） d. Higher interest rates → borrowing becomes more expensive → $I$ and interest-sensitive $C$ fall → $A D$ shifts left. d. 利率上升 → 借贷成本提高 → 投资和对利率敏感的消费下降 → 总需求曲线左移。

e. Faster income growth in other countries → foreigners buy more domestic exports → $NX$ rises → $A D$ shifts right. e. 其他国家收入增长更快 → 外国人购买本国出口商品增多 → 净出口 $NX$ 上升 → 总需求曲线右移。

f. A higher exchange rate (domestic currency appreciates) → exports fall and imports rise → $NX$ falls → $A D$ shifts left. f. 本币汇率升高（本币升值）→ 出口减少、进口增加 → 净出口下降 → 总需求曲线左移。

Extension（拓展） These channels connect open-economy variables (capital flows, exchange rates, foreign income) to domestic output fluctuations via $A D$ . 这些机制把开放经济中的变量（资本流动、汇率、外国收入）与国内产出波动通过总需求联系在一起。

Image/Data Analysis（图像或数据分析） Graphically, rightward shifts (cases b, e) move equilibrium output and often prices up; leftward shifts (c, d, f) move equilibrium output down, possibly causing recession. 在图像上，右移（b、e）会使均衡产出和价格通常上升；左移（c、d、f）会使均衡产出下降，可能引发经济衰退。

Slide 30 — Movements vs. Shifts on the AD Curve（第30页——总需求曲线上的移动与平移）

Knowledge Points (知识点)

Movement from point A to B on $A D_{1}$ （沿同一条总需求曲线从 A 点到 B 点的移动）
Movement from point A to C across $A D_{1}$ and $A D_{2}$ （从 A 点到 C 点的跨曲线变化）

🔹Knowledge Point 1 — Movement from A to B on $A D_{1}$ （A 点到 B 点的移动）

Explanation（解释） A movement from point A to point B along $A D_{1}$ is caused solely by a change in the price level. Real income changes because of this price change, but underlying spending factors are unchanged. 沿着同一条 $A D_{1}$ 从 A 点到 B 点的移动，只能由价格水平变化引起；由于物价变化，实际收入和需求量改变，但各支出决定因素本身并未改变。

Example（例子） If the overall price level rises due to inflation while government purchases, taxes, expectations, and foreign income stay constant, the economy moves from A to B on $A D_{1}$ . 如果出现通货膨胀、总体物价上升，而政府购买、税收、预期、国外收入都保持不变，则经济会沿着 $A D_{1}$ 从 A 点移动到 B 点。

Extension（拓展） Such movements are sometimes called changes in the “quantity of real GDP demanded,” not changes in aggregate demand itself. 这种沿曲线移动通常被称作“需求量的变化”，而不是“总需求的变化”。

Image/Data Analysis（图像或数据分析） In the diagram, A and B lie on the same downward-sloping $A D_{1}$ ; A has lower $P$ and higher $Y$ , B has higher $P$ and lower $Y$ . 在图中，A 与 B 位于同一条向下倾斜的 $A D_{1}$ 上；A 点对应较低的价格水平和较高的实际 GDP，B 点对应较高的价格水平和较低的实际 GDP。

🔹Knowledge Point 2 — Movement from A on $A D_{1}$ to C on $A D_{2}$ （从 A 点到 C 点：总需求曲线的右移）

Explanation（解释） A move from A (on $A D_{1}$ ) to C (on $A D_{2}$ ) indicates a shift of the entire $A D$ curve to the right. At every price level, planned spending is now higher. 从 $A D_{1}$ 上的 A 点到 $A D_{2}$ 上的 C 点表示整条总需求曲线向右平移；在每一个价格水平下，计划支出都比原来更高。

Example（例子） An increase in government purchases, optimistic expectations of future income, or tax cuts that raise disposable income can all shift $A D$ from $A D_{1}$ to $A D_{2}$ , moving the equilibrium from A to C. 政府购买增加、家庭对未来收入更加乐观、减税提高可支配收入等，都可以使总需求从 $A D_{1}$ 右移到 $A D_{2}$ ，从而令均衡由 A 点变为 C 点。

Extension（拓展） This type of shift is what stabilization policy (fiscal or monetary) tries to create when fighting recessions or inflation gaps. 这种曲线平移正是稳定政策（财政或货币政策）在应对衰退缺口或通胀缺口时所要制造的变化。

Image/Data Analysis（图像或数据分析） On the graph, $A D_{2}$ lies to the right of $A D_{1}$ ; point C has the same or higher $P$ but higher $Y$ than A, reflecting stronger aggregate spending. 在图中， $A D_{2}$ 位于 $A D_{1}$ 的右侧；C 点相对于 A 点具有相同或更高的价格水平以及更高的产出，体现了更强的总需求。

Slide 31 — Practice: Long-run Aggregate Supply Determinants（第31页——长期总供给决定因素练习）

Knowledge Points (知识点)

Price level vs. long-run output ( $L R A S$ is vertical)（价格水平与长期总供给的关系）
Real factors that shift $L R A S$ （推动长期总供给曲线平移的真实因素）

🔹Knowledge Point 1 — Higher Price Level and $L R A S$ （更高价格水平对长期总供给的影响）

Explanation（解释） In the long run, $L R A S$ is vertical at potential GDP. A higher price level does not change the economy’s capacity to produce; it just affects nominal prices, not real output at full employment. 在长期内，长期总供给曲线 $L R A S$ 在潜在 GDP 水平处为一条竖直线。价格水平提高并不会改变经济能够生产的最大产出，只是改变名义价格，而不会改变充分就业下的实际产出。

Example（例子） If the price level rises from 115 to 120 while the number of workers, capital stock, and technology are unchanged, potential GDP stays at $20$ 万亿美元， $L R A S$ 不移动。如果价格水平从 115 上升到 120，而劳动、资本和技术都没有变化，则潜在 GDP 仍为 20 万亿美元， $L R A S$ 不发生平移。

Extension（拓展） This is why long-run growth is modeled separately from inflation: growth depends on resources and technology, not on the current price level. 这也是增长分析通常与通货膨胀分开讨论的原因：长期增长取决于资源与技术，而不是当期的物价水平。

Image/Data Analysis（图像或数据分析） In diagrams, different price levels all intersect the same vertical $L R A S$ line at the same real GDP, showing no change in potential output. 在图像中，无论价格水平如何变化，都与同一条竖直的 $L R A S$ 相交于同一实际 GDP 水平，说明潜在产出不受影响。

🔹Knowledge Point 2 — Increases in Labor, Capital, and Technology（劳动、资本与技术对 $L R A S$ 的影响）

Explanation（解释） An increase in the labor force, in the quantity of capital goods, or technological change raises potential GDP and shifts $L R A S$ to the right. 劳动供给增加、资本存量扩大或技术进步都会提高潜在 GDP，使长期总供给曲线整体向右移动。

Example（例子） b. More workers enter the labor force → potential output rises → $L R A S$ shifts right. b. 劳动人口增加 → 潜在产出提高 → $L R A S$ 右移。

c. Firms invest in more machines and factories → capital stock grows → $L R A S$ shifts right. c. 企业大量投资机器与厂房 → 资本存量上升 → $L R A S$ 右移。

d. Technological innovation makes workers more productive → with the same inputs, more output is produced → $L R A S$ shifts right. d. 技术创新提高劳动生产率 → 在同样投入下产出更多 → $L R A S$ 右移。

Extension（拓展） Policies that promote education, R&D, and capital formation are called “supply-side” policies because they aim to shift $L R A S$ right over time. 鼓励教育、人力资本、研发和资本形成的政策被称为“供给侧”政策，因为它们致力于在长期内推动 $L R A S$ 向右移动。

Image/Data Analysis（图像或数据分析） Graphically, the vertical $L R A S$ line moves from $L R A S_{1}$ at $Y_{1}$ to $L R A S_{2}$ at a higher $Y_{2}$ , with the whole AD–AS diagram’s long-run equilibrium following that shift. 在图像中，竖直的 $L R A S$ 由 $L R A S_{1}$ 在 $Y_{1}$ 水平右移到 $L R A S_{2}$ 在更高的 $Y_{2}$ 水平，长期均衡点也随之向右移动。

Slide 32 — Practice: Short-run Aggregate Supply and Its Shifts（第32页——短期总供给曲线及其平移练习）

Knowledge Points (知识点)

Movement along $SR A S$ from A to B（沿着同一条短期总供给曲线从 A 到 B 的移动）
Shift of $SR A S$ from $SR A S_{1}$ to $SR A S_{2}$ and point C（短期总供给曲线平移与 A 到 C 的变化）

🔹Knowledge Point 1 — Movement from A to B on $SR A S_{1}$ （从 A 点到 B 点：沿曲线移动）

Explanation（解释） A move from point A to point B on the same $SR A S_{1}$ is caused by a change in the price level, given fixed nominal input costs and expectations. Firms supply more output in the short run when the price level rises and their costs are slow to adjust. 在相同的 $SR A S_{1}$ 上从 A 点移动到 B 点，是由于价格水平变化引起的；在名义投入成本和预期暂时不变的情况下，物价上升时企业会在短期内增加产出。

Example（例子） If the price level rises from 115 to 117 but wages have not yet been renegotiated, profits increase, and firms move from A to B by producing more. 若价格水平从 115 上升到 117，而工资合同尚未重新谈判，企业盈利提高，就会沿 $SR A S_{1}$ 从 A 点移动到 B 点，增加产出。

Extension（拓展） This reflects sticky wages/prices: short-run quantity supplied can respond to price changes even when long-run capacity is unchanged. 这体现了工资和价格的黏性：即使长期产能不变，短期供给数量仍会对价格变化作出反应。

Image/Data Analysis（图像或数据分析） On the graph, A and B lie on the same upward-sloping $SR A S_{1}$ ; higher $P$ at B corresponds to a higher level of real GDP. 在图中，A 与 B 位于同一条向上倾斜的 $SR A S_{1}$ 上；B 点具有更高的价格水平和更高的实际 GDP。

🔹Knowledge Point 2 — Shift from $SR A S_{1}$ to $SR A S_{2}$ and Point C（从 $SR A S_{1}$ 到 $SR A S_{2}$ ：短期总供给的平移）

Explanation（解释） A move from A on $SR A S_{1}$ to C on $SR A S_{2}$ represents a shift of the short-run aggregate supply curve. This occurs when underlying production conditions change at every price level (e.g., productivity, input prices, expectations). 从 $SR A S_{1}$ 上的 A 点移动到 $SR A S_{2}$ 上的 C 点，表示短期总供给曲线本身发生了平移。这是因为在每一个价格水平下，生产条件发生了系统性变化（如生产率、投入价格或预期的改变）。

Example（例子） If productivity rises or input prices fall (for example, cheaper energy), firms can produce more at each price level; $SR A S$ shifts right from $SR A S_{1}$ to $SR A S_{2}$ , and the economy moves from A to C. 如果生产率提高或投入价格下降（例如能源价格下降），企业在任何给定价格水平下都能提供更多产出；此时 $SR A S$ 从 $SR A S_{1}$ 右移到 $SR A S_{2}$ ，经济从 A 点变为 C 点。

Extension（拓展） Negative supply shocks, such as sudden oil price hikes, would shift $SR A S$ left instead, moving the economy to a point with higher prices and lower output (stagflation). 相反，若发生负向供给冲击，如石油价格突然大幅上涨，则 $SR A S$ 会向左移，使经济处在更高物价、较低产出的“滞胀”状态。

Image/Data Analysis（图像或数据分析） In the figure, $SR A S_{2}$ lies to the right of $SR A S_{1}$ ; C is on $SR A S_{2}$ at a higher output for a given price level than A had on $SR A S_{1}$ , illustrating improved supply conditions. 在图中， $SR A S_{2}$ 位于 $SR A S_{1}$ 的右侧；C 点在给定价格水平下具有比 A 点更高的产出，形象地说明了供给条件改善带来的短期总供给曲线右移。

Slide 33 — Practice: Aggregate Demand Determinants（第27页——总需求决定因素练习）

Knowledge Points (知识点)

Price level vs. quantity of AD（价格水平变化与总需求量变动）
Fiscal & monetary factors and AD shifts（财政与货币因素对总需求曲线的影响）
Foreign income & exchange rate and AD（国外收入与汇率对总需求的影响）
Movement along AD vs. shift of AD（沿着总需求曲线移动与曲线整体移动）

🔹Knowledge Point 1 — Price Level vs. Quantity of AD（价格水平变化与总需求量）

Explanation（解释）

An increase in the price level does not shift the AD curve; it causes a movement up along a given AD curve, so real GDP demanded falls.
价格水平上升不会让 AD 曲线整体移动，只是沿着既有 AD 曲线向上移动，所对应的实际 GDP 需求量减少。

Example（例子）

In question (a), a higher price level makes households feel poorer (wealth effect), raises interest rates, and makes domestic goods relatively more expensive than foreign goods, so real GDP demanded decreases.
题目 (a) 中，价格水平上升：财富效应、利率效应、净出口效应一起作用，使得实际 GDP 需求量减少。

Extension（拓展）

Always link “price level change only” → movement along AD; “anything else” (C, I, G, NX) → shift.
记忆：只要是“单纯价格水平变动”→ 沿曲线移动；任何导致 C、I、G、NX 发生变化的因素 → 曲线整体移动。

Image/Data Analysis（图像或数据分析）

On the AD graph, moving from point A to B on $A D_{1}$ represents a higher price level and lower real GDP, still on the same AD curve.
在图中，从 A 点到 B 点是沿着 $A D_{1}$ 向上移动：价格水平上升，实际 GDP 下降，但仍在同一条 AD 曲线上。

🔹Knowledge Point 2 — Fiscal & Monetary Factors and AD Shifts（财政与货币因素）

Explanation（解释）

Government purchases $G$ and taxes $T$ change planned spending:
- Higher $G$ → AD shifts right.
- Higher income taxes → households’ disposable income ↓ → consumption $C$ ↓ → AD shifts left.
- Higher interest rates $i$ make borrowing more expensive → investment $I$ (and some $C$ ) ↓ → AD shifts left.
政府购买和税收通过改变计划支出影响 AD：
- 政府购买上升 → AD 右移。
- 所得税提高 → 可支配收入减少 → 消费下降 → AD 左移。
- 利率提高 → 借款成本上升 → 投资和部分消费下降 → AD 左移。

Example（例子）

Question (b): higher government purchases → $A D$ shifts right.
Question (c): higher state income taxes → $C$ falls → $A D$ shifts left.
Question (d): higher interest rates → $I$ falls → $A D$ shifts left.
题目 (b) 政府购买增加 → AD 右移；(c) 所得税提高 → AD 左移；(d) 利率提高 → AD 左移。

Extension（拓展）

Think “expansionary fiscal/monetary policy” (↑G, ↓T, ↓i) → AD right; “contractionary” (↓G, ↑T, ↑i) → AD left.
记忆：扩张性财政/货币政策（增 G、减 T、降 i）→ AD 右移；紧缩性 → AD 左移。

Image/Data Analysis（图像或数据分析）

Any of (b)-(d) that increase total spending shift the whole curve from $A D_{1}$ to $A D_{2}$ (right); those that reduce spending shift it back left.
图中 AD 曲线整体从 $A D_{1}$ 移到 $A D_{2}$ ，就是 G、T、i 这类“非价格因素”引起的。

🔹Knowledge Point 3 — Foreign Income, Exchange Rate and AD（国外收入与汇率）

Explanation（解释）

Faster income growth abroad → foreigners buy more of our exports → net exports $NX$ ↑ → AD shifts right.
If the domestic currency appreciates (higher exchange rate in terms given) → our exports become more expensive, imports cheaper → $NX$ ↓ → AD shifts left.
国外收入增长更快 → 外国人多买本国出口 → 净出口上升 → AD 右移。
本币升值（汇率上升）→ 出口变贵、进口变便宜 → 净出口下降 → AD 左移。

Example（例子）

Question (e): faster income growth in other countries → AD right.
Question (f): higher exchange rate (stronger dollar) → AD left.
题目 (e)：国外收入增长更快 → AD 右移；题目 (f)：本币升值 → AD 左移。

Extension（拓展）

Always connect NX changes with “foreign income / exchange rate / foreign preferences / trade policy”.
看到净出口相关问题（国外收入、汇率、关税等）就想到 AD 通过 NX 发生移动。

Image/Data Analysis（图像或数据分析）

On the AD diagram, events (e) and (f) move the curve between $A D_{1}$ and $A D_{2}$ :
- $NX ↑$ → shift right to $A D_{2}$ .
- $NX ↓$ → shift left back to $A D_{1}$ .
在 AD 图上，净出口增加会把曲线从 $A D_{1}$ 推到 $A D_{2}$ ，减少则相反。

🔹Knowledge Point 4 — Movement vs. Shift on AD Graph（沿曲线移动与曲线平移）

Explanation（解释）

Movement A → B on the same AD curve: caused only by a change in price level.
Movement A → C: point C lies on a different AD curve ( $A D_{2}$ ), so it is caused by a change in non-price determinants (C, I, G, NX).
从 A 到 B：同一条 AD 曲线上点的变化，只因价格水平改变；
从 A 到 C：到另一条 AD 曲线上的点，是非价格因素变化导致 AD 曲线整体平移。

Example（例子）

A → B: e.g. inflation rises from 115 to a higher price level with no policy or shocks to C, I, G, NX.
A → C: e.g. government increases spending or central bank cuts interest rates → AD shifts right.
A→B：仅仅是物价上涨；A→C：例如 G 上升或 i 下降引起 AD 右移。

Extension（拓展）

Exam trick: when question asks “movement along AD or shift of AD?” first check whether the price level itself is one of the causes.
做题时先看题目“原因”是不是价格水平本身；是 → 沿曲线移动；不是 → 曲线平移。

Image/Data Analysis（图像或数据分析）

In the given graph, $A D_{1}$ is the darker line and $A D_{2}$ the lighter one:
- A→B: move down along $A D_{1}$ .
- A→C: shift to $A D_{2}$ at the same price level but higher real GDP.
图中深色为 $A D_{1}$ ，浅色为 $A D_{2}$ ：A→B 是沿 $A D_{1}$ 移动，A→C 是在同一价格水平下，AD 右移后的新点。

Slide 34 — Practice: Long-run & Short-run Aggregate Supply（第28页——长期与短期总供给练习）

Knowledge Points (知识点)

Determinants of LRAS（长期总供给的决定因素）
Determinants of SRAS（短期总供给的决定因素）
Movement vs. shift on SRAS graph（沿着 SRAS 移动与 SRAS 平移）

🔹Knowledge Point 1 — Determinants of LRAS（长期总供给决定因素）

Explanation（解释）

LRAS shows potential GDP; it depends on labor, capital, and technology, not on the current price level.
Factors:
- Higher price level → no shift of LRAS (just different point on same vertical line).
- Increase in labor force → LRAS shifts right.
- Increase in capital stock (machines, factories) → LRAS shifts right.
- Technological progress → LRAS shifts right.
长期总供给表示“潜在产出”，取决于劳动、资本和技术，与当前价格水平无关。
- 价格水平上升：LRAS 不移动；
- 劳动力增加：LRAS 右移；
- 资本品数量增加：LRAS 右移；
- 技术进步：LRAS 右移。

Example（例子）

Question “a higher price level”: only moves the economy up along the same LRAS; potential GDP is unchanged.
Questions (b)-(d): more labor, more capital, better technology all raise potential GDP → LRAS right.
题目 (a)：只是沿同一条 LRAS 线上下移动；(b)(c)(d) 则让潜在 GDP 增加，LRAS 向右。

Extension（拓展）

LRAS thinking rule: “anything that changes productive capacity” → shift; “only price level changes” → no shift.
口诀：改变“生产能力”的因素才会移动 LRAS；仅仅是物价变动，LRAS 不动。

Image/Data Analysis（图像或数据分析）

In LRAS diagrams, shifts are shown as vertical lines moving from $L R A S_{1}$ to $L R A S_{2}$ to the right when labor/capital/technology increase.
图中 LRAS 从 $L R A S_{1}$ 向右移到 $L R A S_{2}$ ，表示潜在 GDP 随劳动力、资本或技术进步而提高。

🔹Knowledge Point 2 — Determinants of SRAS（短期总供给决定因素）

Explanation（解释）

SRAS depends on current production costs: wages, energy prices, taxes, productivity, expected future price level, etc.
For the special questions:
- (a) Increase in productivity → unit cost falls → SRAS shifts right.
- (b) Decrease in cost of energy (e.g. cheaper oil, electricity) → production cost falls → SRAS shifts right.
- (c) Decrease in income tax on labor can reduce firms’ labor cost (workers accept lower pre-tax wage) → SRAS shifts right.
短期总供给取决于当前成本（工资、能源价格、税收、生产率、预期物价等）：
- 生产率提高 → 单位成本下降 → SRAS 右移；
- 能源成本下降 → 成本下降 → SRAS 右移；
- 所得税下降（特别是对工资的税）→ 企业用工成本降低 → SRAS 右移。

Example（例子）

Any shock that raises costs (e.g. oil price spike) would shift SRAS left; any that reduces costs (higher productivity, cheaper inputs, lower cost taxes) shifts it right.
成本上升（油价暴涨）→ SRAS 左移；成本下降（技术进步、能源变便宜、减税）→ SRAS 右移。

Extension（拓展）

Always distinguish:
- Cost factors → SRAS;
- Capacity factors (labor, capital, technology trend) → both LRAS and SRAS.
记忆：短期“成本因素”看 SRAS；长期“产能因素”会同时推动 LRAS 和 SRAS。

Image/Data Analysis（图像或数据分析）

On a SRAS graph, a rightward shift from $SR A S_{1}$ to $SR A S_{2}$ corresponds exactly to “productivity ↑ / costs ↓”.
在图中 SRAS 从 $SR A S_{1}$ 右移到 $SR A S_{2}$ ，就是生产率提高或成本下降的图像表达。

🔹Knowledge Point 3 — Movement vs. Shift on SRAS Graph（沿 SRAS 移动与 SRAS 平移）

Explanation（解释）

Movement A → B on the same SRAS curve: caused only by a change in price level, with all cost conditions unchanged.
Movement A → C: C lies on $SR A S_{2}$ , a different curve → caused by a change in production costs or productivity.
从 A 到 B：在同一条 SRAS 上移动，只因为价格水平变动；
从 A 到 C：到另一条 SRAS 上，是成本或生产率等“非价格因素”变化导致 SRAS 平移。

Example（例子）

A → B: price level rises due to higher AD, but wages and input prices haven’t adjusted yet.
A → C: a positive supply shock (e.g. cheaper oil, better technology) shifts SRAS right at any given price level.
A→B：AD 增加推高物价，成本暂时不变；A→C：油价下降或技术进步等正向供给冲击，把 SRAS 整体右移。

Extension（拓展）

Exam rule parallel to AD: “price level only” → movement; “cost/productivity/expectations/resource price” → SRAS shift.
做题时与 AD 同理：只提物价 → 沿 SRAS 移动；提成本、生产率、预期或资源价格 → SRAS 平移。

Image/Data Analysis（图像或数据分析）

In the given SRAS diagram,
- A→B: move up along $SR A S_{1}$ as price level increases.
- A→C: SRAS shifts right to $SR A S_{2}$ , so at the same price level the economy can produce more real GDP.
在给定图中：A→B 是沿 $SR A S_{1}$ 向上移动；A→C 是 SRAS 右移后，在相同价格水平下产出增加的点。

Quartz 4

Explorer

Slide 1 — Aggregate Demand: Learning Objective and Basic Concepts （第1页——总需求：学习目标与基本概念）

Slide 1 — Aggregate Demand: Learning Objective and Basic Concepts （第1页——总需求：学习目标与基本概念）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Aggregate Demand (AD) Curve（总需求曲线）

🔹Knowledge Point 2 — Short-run Aggregate Supply (SRAS) Curve（短期总供给曲线）

🔹Knowledge Point 3 — AD–SRAS Model and Learning Objective（AD–SRAS 模型与学习目标）

Slide 2 — Aggregate Demand and Short-run Aggregate Supply Diagram （第2页——总需求与短期总供给图示）

Knowledge Points (知识点)

🔹Knowledge Point 1 — AD and SRAS in a Diagram（图中的 AD 与 SRAS）

🔹Knowledge Point 2 — Short-run Macroeconomic Equilibrium（短期宏观均衡）

🔹Knowledge Point 3 — Why We Need Macroeconomic Explanations（为何需要宏观层面的解释）

Slide 3 — Why Is the Aggregate Demand Curve Downward Sloping? The Wealth Effect （第3页——为什么总需求曲线向下倾斜？财富效应）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Wealth Effect and Household Consumption（财富效应与家庭消费）

🔹Knowledge Point 2 — Price Level, Real Wealth, and Consumption（物价水平、实际财富与消费）

🔹Knowledge Point 3 — Wealth Effect and the Downward Slope of the AD Curve（财富效应与 AD 曲线向下倾斜）

Slide 4 — The Interest-Rate Effect on Investment （第4页——利率效应与投资）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Interest-Rate Effect（利率效应）

🔹Knowledge Point 2 — Higher Interest Rates and Lower Investment（高利率与较低的投资）

🔹Knowledge Point 3 — Lower Interest Rates and Higher Aggregate Demand（低利率与更高的总需求）

Slide 5 — The International-Trade Effect on Net Exports （第5页——国际贸易效应与净出口）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Net Exports and International-Trade Effect（净出口与国际贸易效应）

🔹Knowledge Point 2 — Higher Domestic Prices and Lower Net Exports（本国物价上升与净出口下降）

🔹Knowledge Point 3 — Lower Domestic Prices and Higher Net Exports（本国物价下降与净出口上升）

Slide 6 — Shifts of the AD Curve versus Movements along It （第6页——总需求曲线的移动与沿曲线移动）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Movements along the AD Curve（沿 AD 曲线的移动）

🔹Knowledge Point 2 — Shifts of the AD Curve（AD 曲线的平移）

🔹Knowledge Point 3 — Categories of AD Shifters（推动 AD 曲线平移的变量类别）

Slide 7 — Changes in Government Policies: Monetary and Fiscal Policy （第7页——政府政策变动：货币政策与财政政策）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Monetary Policy and Aggregate Demand（货币政策与总需求）

🔹Knowledge Point 2 — Fiscal Policy and Aggregate Demand（财政政策与总需求）

🔹Knowledge Point 3 — Policy Mix and Direction of AD Shifts（政策组合与 AD 平移方向）

Slide 8 — Expectations of Households and Firms （第8页——家庭与企业预期）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Household Expectations and Consumption（家庭预期与消费）

🔹Knowledge Point 2 — Firms’ Expectations and Investment（企业预期与投资）

🔹Knowledge Point 3 — Expectations as AD Shifters（预期作为总需求平移因素）

Slide 9 — Changes in Foreign Variables （第9页——国外变量的变化）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Foreign Demand and Domestic Demand for Imports（国外需求与本国进口需求）

🔹Knowledge Point 2 — Relative GDP Growth and Net Exports（相对 GDP 增长与净出口）

🔹Knowledge Point 3 — Exchange Rate Changes and AD（汇率变化与总需求）

Slide 10 — Summary of Factors Shifting the AD Curve （第10页——推动总需求曲线平移的因素总结）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Policy Variables and AD Shifts（政策变量与 AD 平移）

🔹Knowledge Point 2 — Expectations as Shown in the Table（表格中的预期因素）

🔹Knowledge Point 3 — Foreign Variables in the Summary Table（表格中的国外变量）

Slide 11 — Aggregate Supply: Learning Objective （第11页——总供给：学习目标）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Definition of Aggregate Supply（总供给的定义）

🔹Knowledge Point 2 — Short Run vs. Long Run in Aggregate Supply（总供给中的短期与长期）

🔹Knowledge Point 3 — Learning Objective for Aggregate Supply（总供给部分的学习目标）

Slide 12 — The Long-run Aggregate Supply Curve （第12页——长期总供给曲线）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Determinants of Long-run Real GDP（长期实际 GDP 的决定因素）

🔹Knowledge Point 2 — Potential GDP and Full Employment（潜在 GDP 与充分就业）

🔹Knowledge Point 3 — Shape and Interpretation of LRAS（LRAS 曲线的形状与含义）

Slide 13 — Shifts of the Long-run Aggregate Supply Curve （第13页——长期总供给曲线的平移）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Why LRAS Shifts Over Time（LRAS 随时间平移的原因）

🔹Knowledge Point 2 — Potential GDP Growth and LRAS Rightward Shift（潜在 GDP 增长与 LRAS 右移）

🔹Knowledge Point 3 — Image/Data Analysis of LRAS Shifts（LRAS 平移的图像与数据分析）

Slide 14 — The Short-run Aggregate Supply Curve （第14页——短期总供给曲线）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Upward-sloping SRAS Curve（SRAS 曲线向上倾斜）

🔹Knowledge Point 2 — Why Firms Produce More When Prices Rise（价格上升时企业为何多生产）

🔹Knowledge Point 3 — Imperfect Price-level Expectations（价格预期误差与 SRAS）

Slide 15 — Sticky Wages and Prices: Contracts （第15页——工资与价格粘性：合同因素）

Knowledge Points (知识点)

🔹Knowledge Point 1 — Three Reasons for Stickiness（三大粘性原因）

🔹Knowledge Point 2 — What “Sticky” Wages and Prices Mean（“粘性”工资与价格的含义）

🔹Knowledge Point 3 — Contracts, Profits, and SRAS（合同、利润与 SRAS）

Slide 16 — Slow Wage Adjustment and Menu Costs （第16页——工资调整缓慢与菜单成本）

Knowledge Points (知识点)

🔹Knowledge Point 2 — Monetary and External Factors on $A D$ （货币与外部因素对总需求的影响）

🔹Knowledge Point 1 — Movement from A to B on $A D_{1}$ （A 点到 B 点的移动）

🔹Knowledge Point 2 — Movement from A on $A D_{1}$ to C on $A D_{2}$ （从 A 点到 C 点：总需求曲线的右移）

🔹Knowledge Point 1 — Higher Price Level and $L R A S$ （更高价格水平对长期总供给的影响）

🔹Knowledge Point 2 — Increases in Labor, Capital, and Technology（劳动、资本与技术对 $L R A S$ 的影响）