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1、第三十三章总需求与总供给Aggregate Demand and Aggregate Supply11短期经济波动Short-Run Economic Fluctuations经济活动年复一年地波动Economic activity fluctuates from year to year.在大多数年份里，物品与服务的生产是上升的ost years production of goods and servirises.在过去50年，平均来说，经济的生产每年增长约3个百分点。Oage over the past 50 years, productionheU.S. economy has gro

2、wn by about 3 percent per year.在一些年份，正常的增长没能出现，导致了。In some years normal growth does not occur,2causing a re.2关于经济波动的三个关键事实 Three Key Facts About Economic Fluctuations经济波动是不规则和不可的。 Economic fluctuations are irregular and unpredictable.经 中的波动常常被称作经济周期（或译商业周期） Fluctuations he economy are often called t

3、he business cycle.大多数宏观经济变量一起波动。Most macroeconomic variables fluctuatetogether.随着产出下降，失业率上升。As output falls, unemployment rises.4短期经济波动Short-Run Economic Fluctuations是实际GDP下降、收入减少、失业上升的时期A reisriod of declining real GDP, fallinges, and rising unemployment.是严重的A depresis a severe re.33指数（1952=100）短期经

4、济波动一瞥：中国A Look At Short-Run Economic Fluctuations: China(a) 实际GDP450040003500300025002000资料来源：1500中国国内生产总值核算历史资1000料，19521995，中计500年鉴以及作者计算。019671972197719821987199219972002年 份6短期经济波动一瞥A Look At Short-Run Economic Fluctuations(a)Real GDPBillions of实际GDP2000 Dollars$10,000 9,0008,0007,0006,0005,0004,

5、0003,0002,00019651970197519801985 1990 19952000 20055Real GDP4短期经济波动一瞥A Look At Short-Run Economic Fluctuations(b) Investment Spending投资支出Billions of 2000 Dollars$1,5001,000Investment Spending50001965197019751980198519901995200020058关于经济波动的三个关键事实 Three Key Facts About Economic Fluctuations大多数宏观经济变量一

6、起波动。Most macroeconomic variables fluctuate together.大多数衡量某种收入或生产的宏观经济变量几乎同时波动。Most macroeconomic variablest measuresome type ofe or production fluctuate closely together.虽然许多宏观经济变量一起波动，他们波动的幅度并不同。Although many macroeconomic variablesfluctuate together, they fluctuate by different amounts.75指数（1952=1

7、00）中国：GDP、工业生产总值、固定资产投资年增长率的波动1070%60%50%40%30%20%10%0%-10%197819831988199319982003-20%资料来源：五十年统计资料汇编统计年鉴GDP增长率工业总产值增长率 固定资产投资增长率短期经济波动一瞥：中国A Look At Short-Run EconomicFluctuations: China(b) 投资支出900080007000600050004000300020001000019521957196219671972197719821987年 份96短期经济波动一瞥A Look At Short-Run Eco

8、nomic Fluctuations(c) Unemployment Rate失业率Percent ofLabor Force12%10864219651970197519801985199019952000200512Unemployment Rate关于经济波动的三个关键事实 Three Key Facts About Economic Fluctuations随着产出下降，失业上升。As output falls, unemployment rises.实际GDP的变化和失业率的变化呈反向关系。 Changes in real GDP are inversely related to c

9、hangeshe unemployment rate.在时期，失业大幅上升。During times of re, unemployment risessubstantially.117经济波动的基本模型The Basic Mof Economic Fluctuations用两个变量来建立一个模型，以分析短期波动。Two variables are used to develop a mto yze the short-run fluctuations.以实际GDP衡量的经中物品与服务的产出。 The economys output of goods and servi measured by

10、 real GDP.以CPI或GDP平减指数衡量的整体价格水平。 The overall price level measured by the CPI or the GDP deflator.14短期与长期有何不同How the Short Run Differs From the Long Run大多数相信，古典理论描述了长期而不是短期中的世界。Most economists bevet classical theory describes the worldhe long run but nothe short run.货币供给的变化影响长期中的名义变量而非实际变量 Changes he

11、 money supply affect nominal variables but not real variables he long run.货币中性的假设在研究经济的逐年变化时是不恰当的 The amption of monetary neutrality is not appropriate when studying year-to-year changes inthe economy.138经济波动的基本模型The Basic Mof Economic Fluctuations总需求曲线表示家庭、企业或在任一价格水平上想要的物品与服务的数量。The aggregate deman

12、d curve shows the ty of goods and servithouseholds, firms, and theernment want to buy at each price level.16经济波动的基本模型The Basic Mof Economic Fluctuations使用总需求与总供给模型来解释经济活动围绕其长期趋势的短期波动 Economist use the mof aggregate demand and aggregate supply to explain short-run fluctuations in economic activity ar

13、ound its long-run trend.159总需求与总供给Aggregate Demand and Aggregate Supply.Price Level价格水平Aggregate Supply 总供给Equilibrium price level均衡价格水平Aggregate Demand总需求0Equilibriumty of OutputO1u8 tput均衡产出产出数量经济波动的基本模型The Basic Mof Economic Fluctuations总供给曲线表示企业在任一价格水平上生产和销售的物品与服务的数量。The aggregate supply curve s

14、hows thety of goods and servit firms produce and sell at each price level.1710总供需和苹果市场供需的区别苹果平变化，和位置都的需求不需求也不衣服20如果整体的物价水约束线的斜率不会改变，消费者会变化。其加总的会变化。总供需和苹果市场供需的区别（课堂甜点）苹果的价格上升导致苹果的需求下降，这是因为消费者会转移一部分收入到其他商品的消费中。苹果的价格上升导致苹果的供给上升，这是因为厂商此时增加产出更加有利可图。但是，大家千万别忘了，上述逻辑一定是都是指相对价格的变化。总供需曲线的是总体价格水平和需求和供给之间的关系，所有

15、上述微观的供需逻辑在此都不适用。1911总供需和苹果市场供需的区别由此可以体会以下几点。第一、虽然总供需模型从图形上看和苹果的供需完全类似，但是其经济含义完全不同。经济学的学习需要对这种看似相同，实质大异的东西敏感。第二、 熟知的供需曲线背后的经济逻辑既然不能用到总供需图形中，那说明 需要全新的逻辑来建立这个理论。第三、正因为需要全新的理论，在理解后面的理论时就可以感觉到，为什么这个模型的争议这么大？为什么总供给曲线的三个理论要特别强的、令人不舒服的假设条件。22总供需和苹果市场供需的区别苹果平变化，售价和边%,企业的供售价衣服21如果整体的物价水比如增加10%,那么际成本都增加10 给量不变

16、。MC12总需求曲线The Aggregate-Demand Curve.Price LevelP1 P2Aggregate demand0Y1Y2ty of Output2. 增加了物品与服务的需求数量increases thety of goods and 24servidemanded.1. 价格水平的下降A decreaselevel.he price总需求曲线The Aggregate Demand CurveGDP（Y）的四个组成部分了对物品与服务的总需求。The four components of GDP (Y) contribute to the aggregate dema

17、nd foods and servi.Y = C + I + G + NX2313价格水平与消费：效应The Price Level and Consumption: The Wealth Effect价格水平的下降使得消费者感觉更加富有，这反过来鼓励他们支出。A decreasehe price level makes consumers feel more wealthy, whichurn encourages them to spend more.消费支出的上升意味着对物品与服务更大的需求数量。This increase in consumer spending means large

18、rties of goods and servi demanded.26为什么总需求曲线向下倾斜 Why the Aggregate Demand Curve Is Downward Slo价格水平与消费：效应The Price Level and Consumption: The Wealth Effect价格水平与投资：利率效应The Price Level and Investment: Theerest Rate Effect价格水平与净出口：汇率效应The Price Level and Net Exports: The Exchange-Rate Effect2514价格水平与净出

19、口：汇率效应The Price Level and net Exports: The Exchange-Rate Effect当 的价格水平下降导致了 的利率下降，实际汇率就会贬值，这又刺激了 的净出口。When a fallhe U.S. price level causes U.S. erest rates to fall, the real exchange ratedepretes, which stimulates U.S. net exports.净出口支出的增加意味着物品与服务的需求数量更大。The increase in net export spending means a

20、largerty of goods and servidemanded.28价格水平与投资：利率效应The Price Level and Investment:Theerest Rate Effect更低的价格水平降低了利率，这鼓励了对投资品的更大支出。A lowrice level redutheerest rate, which encourages greater spending on investment goods.投资支出的增加意味着物品与服务的需求数量更大。This increase in investment spending means a largerty of goo

21、ds and servidemanded.2715总需求曲线为什么会移动 Why the Aggregate Demand Curve Might Shift来自消费的移动Shifts arising from Consumption来自投资的移动Shifts arising from Investment来自的移动Shifts arising fromernmentPurchases来自净出口的移动Shifts arising from Net Exports30总需求曲线为什么会移动 Why the Aggregate Demand Curve Might Shift总需求曲线向下倾斜，表

22、示价格水平的下降增加了物品与服务总的需求数量。The downward slope of the aggregate demand curve showst a fallhe price level raises the overallty of goods and servidemanded.然而，在给定价格水平上，许多其他影响物品与服务的需求数量。Many other factors, however, affect thety of goods and servidemanded at any given price level.当这些其他中的任一种发生改变，总需求曲线移动。When o

23、ne of these other factors changes, the aggregatedemand curve shifts.2916总供给曲线The Aggregate Supply Curve在长期中，总供给曲线是垂直的。he long run, the aggregate-supply curve is vertical.在短期内，总供给曲线向上倾斜。he short run, the aggregate-supply curve is upwardslo.32总需求曲线的移动Shiftshe Aggregate Demand Curve.Price LevelP1D2Aggr

24、egate demand, D10Y1Y2ty of Outpu31t17长期总供给曲线The Long-Run Aggregate- Supply Curve.Price LevelLong-run aggregate supplyP1P21. 价格水平的改变A changehe servid inprice level the long run.0Natural ratety ofof outputOutput 342. 不影响长期中物品与服务的供给数量does not affect thety of goods and长期总供给曲线The Long-Run Aggregate Suppl

25、y Curve在长期中，经济的物品与服务的生产依赖于它的劳动、资本与自然资源的供给，以及将这些生产要素转化为产品与服务的可行技术。he long-run, an economys production of goodsand servidepends on itpps of labor, capital, and natural resourand on the available technology used to turn these factors of productiono goods and servi.价格水平在长期中不影响这些变量。The price level does n

26、ot affect these variableshelong run.3318长期总供给曲线为什么会移动 Why the Long-Run Aggregate Supply Curve Might Shift任何改变自然产出率的经济变化都会移动长期总供给曲线。Any changehe economyt alters the natural rate of output shifts the long-run aggregate-supply curve.这样的移动可以按照古典模型中影响产出的若干来分类。The shifts may be categorized according to th

27、e various factorshe classical mt affect output.36长期总供给曲线The Long-Run Aggregate Supply Curve长期总供给曲线垂直于自然产出率处。The long-run aggregate supply curve is vertical at the natural rate of output.这一生产水平也被称为潜在产出或充分就业产出。This level of production is also referred to as potential output or full-employment output.3

28、519长期增长与通货膨胀Long-Run Grownd Inflation.Price1. 在长期中，技术Level198019902000进步移动长期总供给he long-run, technological progress shiftsPlong-run aggregate2000supply.P1990P1980AD2000AD1980AD19900YYYty of198019902000Output3. ,导致产出增长leading to growth in output.384. ,和持续的通货膨胀 and ongoing inflation.2. ,货币供给的增长移动总需求and

29、 growthhe money supply shiftsaggregate-demand.长期总供给曲线为什么移动 Why the Long-Run Aggregate Supply Curve Might Shift来自劳动的移动Shifts arising from Labor来自资本的移动Shifts arising from Capital来自自然资源的移动Shifts arising from Natural Resour来自技术知识的移动Shifts arising from Technological Knowledge3720短期总供给曲线为什么向上倾斜Why the Sho

30、rt-Run Aggregate Supply Curve Slopes Upwardhe Short Run在短期内，经济中整体价格水平的上升倾向于增加物品与服务的供给数量。he short run, an increasehe overall level of prihe economy tends to raise thety of goods and servid.价格水平的下降倾向于减少物品与服务的供给数量。A decreasehe level of pritends to reduce thety of goods and servid.40长期增长与通货膨胀Long-Run Gr

31、ownd Inflation短期的产出与价格波动应该被看成是对持续的长期趋势的偏离。Short-run fluctuations in output and price level should be viewed as deviations from the continuing long- run trends.3921短期总供给曲线为什么向上倾斜 Why the Short-Run Aggregate Supply Curve Slopes Upward in the Short Run错觉理论The Misperceptions Theory粘性工资理论The Sticky-Wage

32、Theory粘性价格理论The Sticky-Price Theory42短期总供给曲线The Short-Run Aggregate Supply Curve.Price LevelP1P20Y2Y1Ou ty of tput1. 价格水平的下降A decrease in the price levelShort-run aggregate supplyredu thety of goods and servirun.dhe short2. 减少了短期内物品与服务的供给数量22粘性价格理论The Sticky-Price Theory某些物品与服务的价格为适应经济状况变化所进行的调整是迟缓的

33、。Priof some goods and serviadjust sluggishly in response to changing economic conditions:价格水平的未预料到的下降，留下某些企业的价格超过了合意的水平。An unexpected fallhe price level leaves some firmswith higher-n-desired pri.这会压低销售，引起企业减少物品与服务的生产数量This depresses sales, which indufirms to reducethety of goods and servithey produ

34、ce.44粘性工资理论The Sticky-Wage Theory名义工资的调整是缓慢的，或者说，在短期内是 “粘性的”。Nominal wages are slow to adjust, or are “sticky”he short run:工资并不随着价格水平的下降而立即调整。 Wages do not adjust immediay to a fallhe price level.更低的价格水平使得雇佣产的利润更低。 A lowrice level makes employment and production less profitable.这就导致企业减少物品与服务的供给数量。Th

35、is indufirms to reduce thety of goodsand servid.4323短期总供给曲线为什么向上倾斜 Why the Short-Run Aggregate Supply Curve Slopes Upward in the Short Run所有这三个理论都表明，当实际价格水平背离人们预期的（expected）价格水平时，产量就背离其自然率。用数学公式表述如下：产品供给量自然产量率a(实际价格水平预期价格水平）短期中，预期价格水平难以调整，实际价格水平的上升增加了产品供给量，总供给曲线向上倾斜。长期中，预期价格水平得到调整，以致与实际价格水平相等，总供给曲线垂

36、直于自然产量率处。46错觉理论The Misperceptions Theory总体价格水平的改变，暂时性地误导供给者，让他们在出售自己产出的市场上，看不 在发生什么 Changes he overall price level temporarilymisleadrs about what is happening he markets in which they sell their output:更低的价格水平导致了对相对价格的错觉。 A lowrice level causes misperceptions about relative pri.这种错觉使得供给者减少物品与服务的供给数

37、量。These misperceptions induupprs to decrease thety of goods and servid.4524总供给曲线为什么会移动 Why the Aggregate Supply Curve Might Shift来自劳动力的移动Shifts arising from Labor来自资本的移动Shifts arising from Capital来自自然资源的移动Shifts arising from Natural Resour.来自技术的移动Shifts arising from Technology.来自预期价格水平的移动Shifts aris

38、ing from the Expected Price Level.48短期总供给曲线为什么向上倾斜Why the Short-Run AggregateSupply Curve Slopes Upwardhe Short Run在短期内，而预期价格结果是实际价格下不变降错觉理论供给者自 供给者认 供给者误认为己的产品价格 为其他产品价 自己产品的相下降格不变 对价格下降，从而减少产出粘性工资理论 供给者自 供给者不 供给者由于产己的产品价格 能调整名义工 品价格下降而下降资减少产出粘性价格理论其他供给供给者自供给者自己产者的价格下降己产品的价格品的相对价格无法调整上升，需求下降，从而减少产出

39、。 4725长期均衡The Long-Run EquilibriumPriceLevelLong-runShort-run价格水平aggregateaggregatesupplysupply长期总供给短期总供给EquilibriumAprice均衡价格总需求 Aggregate Demand0Natural rate ofty ofoutput 自然产出率Out50put产量总供给曲线为什么会移动 Why the Aggregate Supply Curve Might Shift预期价格水平的上升减少了物品与服务的供给数量，将短期总供给曲线向左移动。An increasehe expecte

40、d price level reduthe ty of goods and servid and shiftsthe short-run aggregate supply curve to the left.预期价格水平的下降增加了物品与服务的供给数量，将短期总供给曲线向右移动。A decreasehe expected price level raises the ty of goods and servid and shiftsthe short-run aggregate supply curve to the right.4926总需求的收缩A Contraction in Aggre

41、gate Demand.PriceLevelLong-runShort-run aggregate aggregatesupply, AS1supplyAS2P1AP2BP3CAggregateADdemand, AD10Y2Y12ty of4. 产出回到其自然率上 and output returnsto its natural rate.Output1. 总需求减少A decrease in aggregate demand3. 但是随着时间推移，短期总供给曲线移动 but over time, the short-run aggregate- supply curve shifts2.

42、导致产出在短期内下降 causes output to fall he short run总需求移动Shifts in Aggregate Demand在短期内，总需求的移动导致经济中物品与服务的产出发生波动。he short run, shifts in aggregate demand cause fluctuationshe economys output of goods and servi.在长期中，总需求的移动影响整体的价格水平但不影响产出。he long run, shifts in aggregate demand affect the overall price level

43、but do not affect output.5127总供给的不利移动An Adverse Shift in Aggregate Supply.1. 短期总供给曲线的不利移动 Price LevelP2 P10Y2Y1ty of Output542. 导致产出下降 causes output to fall3. 和价格水平上升and the pricelevel to rise.Long-run aggregate supplyBAn adverse shifthe short- run aggregate-supply curve AS2Short-run aggregate suppl

44、y, AS1AAggregate demand总供给的不利移动An Adverse Shift in Aggregate Supply总供给的某个决定的下降将曲线。A decrease in one of the determinants of aggregate supply shifts the curve to the left:产出下降到自然率之下。Output falls below the natural rate of employment.失业增加 Unemployment rises.价格上升 The price level rises.5328对于的政策反应Policy R

45、esponses to Re政策制定者对 的反应可以是以下方式之一 Policymakers may respond to a rein one of the following ways:什么也不做，等待价格和工资的调整。Do nothing and wait for priand wages to adjust.采取行动，通过货币与财政政策来增加总需求。Take action to increase aggregate demand by usingmonetary and fiscal policy.56滞胀Stagflation总供给的不利移动导致滞胀和通货膨胀并存。Adverse s

46、hifts in aggregate supply cause stagflationa combination of reand inflation.产出下降，价格上升。Output falls and pririse.政策制订者能够影响总需求，但不能同时抵消这两种不利的影响。Policymakers who can influence aggregate demandcannot offset both of these adverse effects simultaneously.5529总供给移动的效应The Effects of a Shift in Aggregate Supply

47、总供给的移动可能引起滞胀与通货膨胀并存。Shifts in aggregate supply can cause stagflation a combination of reand inflation.政策制定者能够影响总需求，却不能同时抵消这两种不利的影响。Policymakers who can influence aggregate demand cannot offset both of these adverse effects simultaneously.58适应总供给的不利移动modating an Adverse Shift in Aggregate Supply.Pric

48、e LevelLong-runaggregate AS2Short-run supplyaggregatesupply, AS1P3CP2AP14. 但是保持产AD2出处于自然率but keepsAggregate demand, AD1outpuits0 natural rate.Natural ratety ofof outputOutput573.这会引起价格上升 which causes the price level to rise2. 政策制定者可以通过扩张总需求来适应这一移动 policymakers canmodate the shift by expanding aggreg

49、ate demand1. 当短期总供给减少When short-run aggregate supply falls30总结Summary使用总需求与总供给模型来分析短期经济波动。Economistsyze short-run economic fluctuations using the aggregate demand and aggregate supply m.按照总需求与总供给模型，物品与服务的产出和整体价格水平做出调整，以平衡总需求与总供给。According to the mof aggregate demand and aggregate supply, the output of goods and servia