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12SHORT-RUNECONOMICFLUCTUATIONS短期经济波动Copyright©2004South-Western33AggregateDemandandAggregateSupply总需求与总供给Copyright©2004South-WesternShort-RunEconomicFluctuations•Economicactivityfluctuatesfromyeartoyear.•Inmostyearsproductionofgoodsandservicesrises.•Onaverageoverthepast50years,productionintheU.S.economyhasgrownbyabout3percentperyear.•Insomeyearsnormalgrowthdoesnotoccur,causingarecession.Copyright©2004South-Western短期经济波动经济活动每年都有波动。在大多数年份，物品与劳务的产量增加了。在过去的50年间，美国经济的产量平均每年增长3%左右。在一些年份，并没有出现这种正常增长，导致衰退。Copyright©2004South-WesternShort-RunEconomicFluctuations短期经济波动•Arecessionisaperiodofdecliningrealincomes,andrisingunemployment.衰退——实际GDP下降和失业增加的时期。•Adepressionisasevererecession.萧条——严重的衰退。Copyright©2004South-WesternTHREEKEYFACTSABOUTECONOMICFLUCTUATIONS•Economicfluctuationsareirregularandunpredictable.•Fluctuationsintheeconomyareoftencalledthebusinesscycle.•Mostmacroeconomicvariablesfluctuatetogether.•Asoutputfalls,unemploymentrises.Copyright©2004South-Western关于经济波动的三个事实经济波动是无规律的和无法预测的。经济中的波动通常被称为经济周期。大多数宏观经济变量同时波动。随着产量减少，失业增加。Figure1ALookAtShort-RunEconomicFluctuationsBillionsof1996DollarsRealGDP(a)RealGDP$10,0009,0008,0007,0006,0005,0004,0003,0002,00019651970197519801985199019952000图1.观察短期经济波动1996的10亿美元RealGDP(a)实际GDP$10,0009,0008,0007,0006,0005,0004,0003,0002,00019651970197519801985199019952000Copyright©2004South-WesternTHREEKEYFACTSABOUTECONOMICFLUCTUATIONS•Mostmacroeconomicvariablesfluctuatetogether.•Mostmacroeconomicvariablesthatmeasuresometypeofincomeorproductionfluctuatecloselytogether.•Althoughmanymacroeconomicvariablesfluctuatetogether,theyfluctuatebydifferentamounts.Copyright©2004South-Western关于经济波动的三个事实大多数宏观经济变量一起波动。大多数衡量某种收入或产出的宏观经济变量同时波动。尽管很多宏观经济变量一起波动，但是它们波动的大小并不同。Figure1ALookAtShort-RunEconomicFluctuationsBillionsof1996Dollars(b)InvestmentSpending$1,8001,6001,4001,2001,00080060040020019651970197519801985199019952000Investmentspending图1.观察短期经济波动(b)投资支出$1,8001,6001,4001,2001,00080060040020019651970197519801985199019952000Investmentspending1996的10亿美元Copyright©2004South-WesternTHREEKEYFACTSABOUTECONOMICFLUCTUATIONS•Asoutputfalls,unemploymentrises.•ChangesinrealGDPareinverselyrelatedtochangesintheunemploymentrate.•Duringtimesofrecession,unemploymentrisessubstantially.Copyright©2004South-Western关于经济波动的三个事实随着产量减少，失业增加。实际GDP的变化与失业率的变化是反向相关的。在衰退期间，失业率大幅上升。Figure1ALookAtShort-RunEconomicFluctuationsPercentofLaborForce(c)UnemploymentRate02468101219651970197519801985199019952000UnemploymentrateCopyright©2004South-Western图1.观察短期经济波动劳动力的百分比(c)失业率02468101219651970197519801985199019952000UnemploymentrateCopyright©2004South-WesternEXPLAININGSHORT-RUNECONOMICFLUCTUATIONS•HowtheShortRunDiffersfromtheLongRun•Mosteconomistsbelievethatclassicaltheorydescribestheworldinthelongrunbutnotintheshortrun.•Changesinthemoneysupplyaffectnominalvariablesbutnotrealvariablesinthelongrun.•Theassumptionofmonetaryneutralityisnotappropriatewhenstudyingyear-to-yearchangesintheeconomy.Copyright©2004South-Western解释短期经济波动•长期与短期有什么不同•大多数经济学家认为，古典经济理论描述长期世界，并不描述短期世界。•在长期中，货币供给的变化影响名义变量，而不影响实际变量。•在研究逐年的经济变动时，货币中性的假设就不再适用了。Copyright©2004South-WesternTheBasicModelofEconomicFluctuations•Twovariablesareusedtodevelopamodeltoanalyzetheshort-runfluctuations.•Theeconomy’soutputofgoodsandservicesmeasuredbyrealGDP.•TheoverallpricelevelmeasuredbytheCPIortheGDPdeflator.Copyright©2004South-Western经济波动的基本模型两个变量被用来建立模型分析短期经济波动。用实际GDP衡量的经济中的物品与劳务的产量。用CPI或GDP平减指数衡量的物价总水平。Copyright©2004South-WesternTheBasicModelofEconomicFluctuations经济波动的基本模型•TheBasicModelofAggregateDemandandAggregateSupply总需求与总供给基本模型•Economistusethemodelofaggregatedemandandaggregatesupplytoexplainshort-runfluctuationsineconomicactivityarounditslong-runtrend.经济学家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的模型。Copyright©2004South-WesternTheBasicModelofEconomicFluctuations经济波动的基本模型•TheBasicModelofAggregateDemandandAggregateSupply总需求与总供给基本模型•Theaggregate-demandcurveshowsthequantityofgoodsandservicesthathouseholds,firms,andthegovernmentwanttobuyateachpricelevel.总需求曲线——一条表示在每一种物价水平时家庭、企业和政府想要购买的物品与劳务量的曲线。Copyright©2004South-WesternTheBasicModelofEconomicFluctuations经济波动的基本模型•TheBasicModelofAggregateDemandandAggregateSupply总需求与总供给基本模型•Theaggregate-supplycurveshowsthequantityofgoodsandservicesthatfirmschoosetoproduceandsellateachpricelevel.总供给曲线——一条表示在每一种物价水平下企业选择生产并销售的物品与劳务量的曲线。Figure2AggregateDemandandAggregateSupply...QuantityofOutputPriceLevel0AggregatesupplyAggregatedemandEquilibriumoutputEquilibriumpricelevel图2.总需求与总供给…产量物价水平0总供给总需求均衡产量均衡物价水平Copyright©2004South-WesternTheAggregateDemandCurve总需求曲线ThefourcomponentsofGDP(Y)contributetotheaggregatedemandforgoodsandservices.GDP(Y)的四个组成部分对物品与劳务的总需求做贡献。Y=C+I+G+NXFigure3TheAggregate-DemandCurve...QuantityofOutputPriceLevel0AggregatedemandPYY2P21.Adecreaseinthepricelevel...2....increasesthequantityofgoodsandservicesdemanded.图3.总需求曲线…产量物价水平0总需求PYY2P21.物价水平下降...2.…物品与劳务量增加Copyright©2004South-WesternWhytheAggregate-DemandCurveIsDownwardSloping•ThePriceLevelandConsumption:TheWealthEffect•ThePriceLevelandInvestment:TheInterestRateEffect•ThePriceLevelandNe