Chapter_05AggregateSupplyandDemand(宏观经济学,多

5-15-2Chapter5AggregateSupplyandDemand•Item•Item•Item•Etc.McGraw-Hill/IrwinMacroeconomics,10e©2008TheMcGraw-HillCompanies,Inc.,AllRightsReserved.5-3Introduction•Thelastfewchaptershavedetailedmodelsoflongruneconomicgrowthnowturntoshortrunfluctuationsintheeconomythatconstitutethebusinesscycle•TheAS/ADmodelisthebasicmacroeconomictoolforstudyingoutputfluctuationsandthedeterminationofthepricelevelandtheinflationrate•Canbeusedtoexplainhowtheeconomydeviatesfromapathofsmoothgrowthovertime,andtoexploretheconsequencesofgovernmentpoliciesintendedtoreduceunemploymentandoutputfluctuations,andmaintainstableprices5-4ASandAD•Aggregatesupplycurvedescribes,foreachgivenpricelevel,thequantityofoutputfirmsarewillingtosupply•Upwardslopingsincefirmsarewillingtosupplymoreoutputathigherprices•Aggregatedemandcurveshowsthecombinationsofthepricelevelandthelevelofoutputatwhichthegoodsandmoneymarketsaresimultaneouslyinequilibrium•Downwardslopingsincehigherpricesreducethevalueofthemoneysupply,whichreducesthedemandforoutput•IntersectionofASandADcurvesdeterminestheequilibriumlevelofoutputandpricelevel5-5AS,AD,andEquilibrium•ASandADintersectatpointEinFigure5-1Equilibrium:AS=AD•EquilibriumoutputisY0•Observedlevelofoutputintheeconomyatparticularpointintime•EquilibriumpricelevelisP0•Observedpricelevelintheeconomyatparticularpointintime[InsertFigure5-1here]5-6AS,AD,andEquilibrium•ShiftsineithertheASorADscheduleresultsinachangeintheequilibriumlevelofpricesandoutput•IncreaseinADincreaseinPandY•DecreaseinADdecreaseinPandY•IncreaseinASdecreaseinPandincreaseinY•DecreaseinASincreaseinPanddecreaseinY[InsertFigure5-2here]Figure5-2illustratesanincreaseinADresultingfromanincreaseinmoneysupply.5-7AS,AD,andEquilibriumTheamountoftheincrease/decreaseinPandYafterashiftineitheraggregatesupplyoraggregatedemanddependson:1.TheslopeoftheAScurve2.TheslopeoftheADcurve3.TheextentoftheshiftofAS/AD[InsertFigure5-3here]Figure5-3showstheresultofanadverseASshock:ASY,P5-8ClassicalSupplyCurve•Theclassicalsupplycurveisvertical,indicatingthatthesameamountofgoodswillbesupplied,regardlessofprice[Figure5-4(b)]•Basedupontheassumptionthatthelabormarketisinequilibriumwithfullemploymentofthelaborforce•Thelevelofoutputcorrespondingtofullemploymentofthelaborforce=potentialGDP,Y*[InsertFigure5-4here]LongrunversionoftheAScurve5-9ClassicalSupplyCurve•Y*growsovertimeastheeconomyaccumulatesresourcesandtechnologyimprovesAScurvemovestotheright•ThegrowththeorymodelsdescribedinearlierchaptersexplainthelevelofY*inaparticularperiod•Y*is“exogenouswithrespecttothepricelevel”illustratedasaverticallinesincegraphedintermsofthepricelevel[InsertFigure5-5here]5-10KeynesianSupplyCurve•TheKeynesiansupplycurveishorizontal,indicatingfirmswillsupplywhateveramountofgoodsisdemandedattheexistingpricelevel[Figure5-4(a)]•Sinceunemploymentexists,firmscanobtainanyamountoflaboratthegoingwagerate•Sinceaveragecostofproductiondoesnotchangeasoutputchanges,firmswillingtosupplyasmuchasisdemandedattheexistingpricelevel[InsertFigure5-4here,again]5-11KeynesianSupplyCurve•IntellectualgenesisoftheKeynesianAScurveisfoundintheGreatDepression,whenitseemedfirmscouldincreaseproductionwithoutincreasingPbyputtingidleKandNtowork•Additionally,pricesareviewedas“sticky”intheshortrun,orfirmsarereluctanttochangepricesandwageswhendemandshifts•Insteadfirmsincrease/decreaseoutputinresponsetodemandshift=flatAScurveintheshortrunShortrunversionoftheAScurve5-12FrictionalUnemploymentandtheNaturalRateofUnemployment•Takenliterally,theclassicalmodelimpliesthatthereisnoinvoluntaryunemploymenteveryonewhowantstoworkisemployed•Inrealitythereissomeunemploymentduetofrictionsinthelabormarket(Ex.Someoneisalwaysmovingandlookingforanewjob)•Theunemploymentrateassociatedwiththefullemploymentlevelofoutputisthenaturalrateofunemployment•Naturalrateofunemploymentistherateofunemploymentarisingfromnormallabormarketfrictionsthatexistwhenthelabormarketisinequilibrium5-13ASandthePriceAdjustmentMechanism•AScurvedescribesthepriceadjustmentmechanismwithintheeconomy•Figure5-6showstheSRAScurveinblackandtheLRASingreen,andtheadjustmentfromtheSRtotheLR•TheAScurveisdefinedbytheequation:(1)where•Pt-1isthepricelevelnextperiod•Ptisthepriceleveltoday•Y*ispotentialoutput[InsertFigure5-6here])](1[*1YYPPtt5-14ASandthePriceAdjustmentMechanism(1)•Ifoutputisabovepotential(YY*),priceswillincreaseandbehighernextperiod•Ifoutputisbelowpotential(YY*),priceswillfallandbelowernextperiod•Priceswillcontinuetorise/fallovertimeuntilY=Y*•Today’spriceequalstomorrow’siifoutputequalspotential(ignoringpriceexpectations)•ThedifferencebetweenGDPandpotentialGDP,Y-Y*,iscalledtheoutputgap[InsertFigure5-6here])](1[*1YYPPtt5-15ASandthePriceAdjustmentMechanism(1)•TheupwardshiftinghorizontallinesinFigure5-6(b)correspondtosuccessivesnapshotsofequation(1)•Beginningwiththehorizontalblacklineattimet=0,atYY*,pricewillbehigher(ASshiftingup)byt=1•ProcesscontinuesuntilY=Y*[InsertFigure5-6here])](1[*1YYPPtt5-16ASandthePriceAdjustmentMechanism(1)•Thespeedofthepriceadjustmentmechanismiscontrol