宏观经济学课件13.ppt
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宏观经济学课件13.ppt
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macroeconomicsfiftheditionN.GregoryMankiwPowerPointSlidesbyRonCronovichmacro2002WorthPublishers,allrightsreservedCHAPTERTHIRTEENAggregateSupplyCHAPTER13CHAPTER13AggregateSupplyAggregateSupplyLearningobjectivesthreemodelsofaggregatesupplyinwhichoutputdependspositivelyonthepricelevelintheshortruntheshort-runtradeoffbetweeninflationandunemploymentknownasthePhillipscurve1CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThreemodelsofaggregatesupply1.Thesticky-wagemodel2.Theimperfect-informationmodel3.Thesticky-pricemodelAllthreemodelsimply:
naturalrateofoutputapositiveparametertheexpectedpriceleveltheactualpricelevelagg.output2CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesticky-wagemodelAssumesthatfirmsandworkersnegotiatecontractsandfixthenominalwagebeforetheyknowwhatthepricelevelwillturnouttobe.Thenominalwage,W,theysetistheproductofatargetrealwage,andtheexpectedpricelevel:
3CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesticky-wagemodelIfitturnsoutthatthenunemploymentandoutputareattheirnaturalratesRealwageislessthanitstarget,sofirmshiremoreworkersandoutputrisesaboveitsnaturalrateRealwageexceedsitstarget,sofirmshirefewerworkersandoutputfallsbelowitsnaturalrate4CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesticky-wagemodelImpliesthattherealwageshouldbecounter-cyclical,itshouldmoveintheoppositedirectionasoutputoverthecourseofbusinesscycles:
Inbooms,whenPtypicallyrises,therealwageshouldfall.Inrecessions,whenPtypicallyfalls,therealwageshouldrise.Thispredictiondoesnotcometrueintherealworld:
6CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThecyclicalbehavioroftherealwagePercentagechangeinrealwagePercentagechangeinrealGDP1982197519931992196019961999199719981979197019801991197419901984200019721965-3-2-101237865443210-1-2-3-4-57CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyTheimperfect-informationmodelAssumptions:
allwagesandpricesperfectlyflexible,allmarketscleareachsupplierproducesonegood,consumesmanygoodseachsupplierknowsthenominalpriceofthegoodsheproduces,butdoesnotknowtheoverallpricelevel8CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyTheimperfect-informationmodelSupplyofeachgooddependsonitsrelativeprice:
thenominalpriceofthegooddividedbytheoverallpricelevel.Supplierdoesntknowpricelevelatthetimeshemakesherproductiondecision,sousestheexpectedpricelevel,Pe.SupposePrisesbutPedoesnot.Thensupplierthinksherrelativepricehasrisen,sosheproducesmore.Withmanyproducersthinkingthisway,YwillrisewheneverPrisesabovePe.9CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesticky-pricemodelReasonsforstickyprices:
long-termcontractsbetweenfirmsandcustomersmenucostsfirmsdonotwishtoannoycustomerswithfrequentpricechangesAssumption:
Firmssettheirownprices(e.g.asinmonopolisticcompetition)10CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesticky-pricemodelAnindividualfirmsdesiredpriceiswherea0.Supposetwotypesoffirms:
firmswithflexibleprices,setpricesasabovefirmswithstickyprices,mustsettheirpricebeforetheyknowhowPandYwillturnout:
11CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesticky-pricemodelAssumefirmsw/stickypricesexpectthatoutputwillequalitsnaturalrate.Then,Toderivetheaggregatesupplycurve,wefirstfindanexpressionfortheoverallpricelevel.Letsdenotethefractionoffirmswithstickyprices.Then,wecanwritetheoverallpricelevelas12CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesticky-pricemodelSubtract(1s)Pfrombothsides:
pricesetbyflexiblepricefirmspricesetbystickypricefirmsDividebothsidesbys:
13CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesticky-pricemodelHighPeHighPIffirmsexpecthighprices,thenfirmswhomustsetpricesinadvancewillsetthemhigh.Otherfirmsrespondbysettinghighprices.HighYHighPWhenincomeishigh,thedemandforgoodsishigh.Firmswithflexiblepricessethighprices.Thegreaterthefractionofflexiblepricefirms,thesmallerissandthebiggeristheeffectofYonP.14CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesticky-pricemodelFinally,deriveASequationbysolvingforY:
15CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesticky-pricemodelIncontrasttothesticky-wagemodel,thesticky-pricemodelimpliesaprocyclicalrealwage:
Supposeaggregateoutput/incomefalls.Then,Firmsseeafallindemandfortheirproducts.Firmswithstickypricesreduceproduction,andhencereducetheirdemandforlabor.Theleftwardshiftinlabordemandcausestherealwagetofall.16CHAPTER13CHAPTER13AggregateSupplyAggregateSupplySummary&implicationsEachofthethreemodelsofagg.supplyimplytherelationshipsummarizedbytheSRAScurve&equationYPLRASSRAS17CHAPTER13CHAPTER13AggregateSupplyAggregateSupplySummary&implicationsSupposeapositiveADshockmovesoutputaboveitsnaturalrateandPabovethelevelpeoplehadexpected.YPLRASSRAS1SRAS2AD1AD2Overtime,Perises,SRASshiftsup,andoutputreturnstoitsnaturalrate.18CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyInflation,Unemployment,andthePhillipsCurveThePhillipscurvestatesthatdependsonexpectedinflation,ecyclicalunemployment:
thedeviationoftheactualrateofunemploymentfromthenaturalratesupplyshocks,where0isanexogenousconstant.19CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyDerivingthePhillipsCurvefromSRAS20CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThePhillipsCurveandSRASSRAScurve:
outputisrelatedtounexpectedmovementsinthepricelevelPhillipscurve:
unemploymentisrelatedtounexpectedmovementsintheinflationrate21CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyAdaptiveexpectationsAdaptiveexpectations:
anapproachthatassumespeopleformtheirexpectationsoffutureinflationbasedonrecentlyobservedinflation.Asimpleexample:
Expectedinflation=lastyearsactualinflationThen,theP.C.becomes22CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyInflationinertiaInthisform,thePhillipscurveimpliesthatinflationhasinertia:
Intheabsenceofsupplyshocksorcyclicalunemployment,inflationwillcontinueindefinitelyatitscurrentrate.Pastinflationinfluencesexpectationsofcurrentinflation,whichinturninfluencesthewages&pricesthatpeopleset.23CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyTwocausesofrising&fallinginflationcost-pushinflation:
inflationresultingfromsupplyshocks.Adversesupplyshockstypicallyraiseproductioncostsandinducefirmstoraiseprices,“pushing”inflationup.demand-pullinflation:
inflationresultingfromdemandshocks.Positiveshockstoaggregatedemandcauseunemploymenttofallbelowitsnaturalrate,which“pulls”theinflationrateup.24CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyGraphingthePhillipscurveIntheshortrun,policymakersfaceatrade-offbetweenandu.uTheshort-runPhillipsCurve25CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyShiftingthePhillipscurvePeopleadjusttheirexpectationsovertime,sothetradeoffonlyholdsintheshortrun.uE.g.,anincreaseineshiftstheshort-runP.C.upward.26CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesacrificeratioToreduceinflation,policymakerscancontractagg.demand,causingunemploymenttoriseabovethenaturalrate.ThesacrificeratiomeasuresthepercentageofayearsrealGDPthatmustbeforegonetoreduceinflationby1percentagepoint.Estimatesvary,butatypicaloneis5.27CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesacrificeratioSupposepolicymakerswishtoreduceinflationfrom6to2percent.Ifthesacrificeratiois5,thenreducinginflationby4pointsrequiresalossof45=20percentofoneyearsGDP.Thiscouldbeachievedseveralways,e.g.reduceGDPby20%foroneyearreduceGDPby10%foreachoftwoyearsreduceGDPby5%foreachoffouryearsThecostofdisinflationislostGDP.OnecoulduseOkunslawtotranslatethiscostintounemployment.28CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyRationalexpectationsWaysofmodelingtheformationofexpectations:
adaptiveexpectations:
Peoplebasetheirexpectationsoffutureinflationonrecentlyobservedinflation.rationalexpectations:
Peoplebasetheirexpectationsonallavailableinformation,includinginformationaboutcurrentandprospectivefuturepolicies.29CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyPainlessdisinflation?
Proponentsofrationalexpectationsbelievethatthesacrificeratiomaybeverysmall:
Supposeu=unand=e=6%,andsupposetheFedannouncesthatitwilldowhateverisnecessarytoreduceinflationfrom6to2percentassoonaspossible.Iftheannouncementiscredible,thenewillfall,perhapsbythefull4points.Then,canfallwithoutanincreaseinu.30CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesacrificeratiofortheVolckerdisinflation1981:
=9.7%1985:
=3.0%yearuunuun19829.5%6.0%3.5%19839.56.03.519847.46.01.419857.16.01.1Total9.5%Totaldisinflation=6.7%31CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThesacrificeratiofortheVolckerdisinflationPreviousslide:
inflationfellby6.7%totalof9.5%ofcyclicalunemploymentOkunslaw:
each1percentagepointofunemploymentimplieslostoutputof2percentagepoints.So,the9.5%cyclicalunemploymenttranslatesto19.0%ofayearsrealGDP.Sacrificeratio=(lostGDP)/(totaldisinflation)=19/6.7=2.8percentagepointsofGDPwerelostforeach1percentagepointreductionininflation.32CHAPTER13CHAPTER13AggregateSupplyAggregateSupplyThenaturalratehypothesisOuranalysisofthec
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