曼昆宏观经济学第三十四章

34TheInfluenceofMonetaryandFiscalPolicyonAggregateDemandTheburningissue•TheoryofliquiditypreferenceKeynes'stheorythattheinterestrateadjuststobringmoneysupplyandmoneydemandintobalance.TheTheoryofLiquidityPreference•Keynesdevelopedthetheoryofliquiditypreferenceinordertoexplainwhatfactorsdeterminetheeconomy’sinterestrate.•Accordingtothetheory,theinterestrateadjuststobalancethesupplyanddemandformoney.Theoverview•Theaggregatedemandcurveslopesdownwardforthreereasons:–Thewealtheffect–Theinterest-rateeffect–Theexchange-rateeffectHowmonetarypolicyinfluencesaggregatedemand?Theoverview•FortheU.S.economy,themostimportantreasonforthedownwardslopeoftheaggregate-demandcurveistheinterest-rateeffect.“Irrationalexuberance.”-----thatwashowFederalReserveChairmanAlanGreenspanoncedescribedtheboomingstockmarketofthelate1990s.TheideaintangibleWhytheFedwatchesthestockmarket?Aboomingstockmarketexpandstheaggregatedemandforgoodsandservices.whenthestockmarketbooms,householdsbecomewealthier,andthisincreasedwealthstimulatesconsumerspending.ariseinstockpricesmakesitmoreattractiveforfirmstosellnewsharesofstock,andthisstimulatesinvestmentspending.Theoppositeoccurswhenthestockmarketfalls.spendingonconsumptionandinvestmentdeclines,depressingaggregatedemandandpushingtheeconomytowardsrecession.Figure1EquilibriumintheMoneyMarketQuantityofMoneyInterestRate0MoneydemandQuantityfixedbytheFedMoneysupplyr2M2dMdr1EquilibriuminterestrateCopyright©2004South-WesternFigure2TheMoneyMarketandtheSlopeoftheAggregate-DemandCurveQuantityofMoneyQuantityfixedbytheFed0InterestRateMoneydemandatpricelevelP2,MD2MoneydemandatpricelevelP,MDMoneysupply(a)TheMoneyMarket(b)TheAggregate-DemandCurve3....whichincreasestheequilibriuminterestrate...2....increasesthedemandformoney...QuantityofOutput0PriceLevelAggregatedemandP2Y2YP4....whichinturnreducesthequantityofgoodsandservicesdemanded.1.Anincreaseinthepricelevel...rr2Copyright©2004South-WesternFigure3AMonetaryInjectionMS2Moneysupply,MSAggregatedemand,ADYYPMoneydemandatpricelevelPAD2QuantityofMoney0InterestRaterr2(a)TheMoneyMarket(b)TheAggregate-DemandCurveQuantityofOutput0PriceLevel3....whichincreasesthequantityofgoodsandservicesdemandedatagivenpricelevel.2....theequilibriuminterestratefalls...1.WhentheFedincreasesthemoneysupply...Copyright©2004South-WesternThecloseAggregateDemand•Manyfactorsinfluenceaggregatedemandbesidesmonetaryandfiscalpolicy.•Inparticular,desiredspendingbyhouseholdsandbusinessfirmsdeterminestheoveralldemandforgoodsandservices.AggregateDemand•Whendesiredspendingchanges,aggregatedemandshifts,causingshort-runfluctuationsinoutputandemployment.•Monetaryandfiscalpolicyaresometimesusedtooffsetthoseshiftsandstabilizetheeconomy.Contents•Howmonetarypolicyinfluencesaggregatedemand?-theoryofliquiditypreference-theDownwardSlopeoftheAggregateDemandCurve-changesinthemoneysupply•Howfiscalpolicyinfluencesaggregatedemand?-changesinthegovernmentpurchases-multipliereffect-crowding-outeffect-changesintaxes•Usingpoliciestostabilizetheeconomy-automaticstabilizersHOWMONETARYPOLICYINFLUENCESAGGREGATEDEMAND•Theaggregatedemandcurveslopesdownwardforthreereasons:–Thewealtheffect–Theinterest-rateeffect–Theexchange-rateeffect•FortheU.S.economy,themostimportantreasonforthedownwardslopeoftheaggregate-demandcurveistheinterest-rateeffect.TheTheoryofLiquidityPreference•Keynesdevelopedthetheoryofliquiditypreferenceinordertoexplainwhatfactorsdeterminetheeconomy’sinterestrate.•Accordingtothetheory,theinterestrateadjuststobalancethesupplyanddemandformoney.•MoneySupply–ThemoneysupplyiscontrolledbytheFedthrough:•Open-marketoperations•Changingthereserverequirements•Changingthediscountrate–BecauseitisfixedbytheFed,thequantityofmoneysupplieddoesnotdependontheinterestrate.–Thefixedmoneysupplyisrepresentedbyaverticalsupplycurve.•MoneyDemand–Moneydemandisdeterminedbyseveralfactors.•Accordingtothetheoryofliquiditypreference,oneofthemostimportantfactorsistheinterestrate.•Peoplechoosetoholdmoneyinsteadofotherassetsthatofferhigherratesofreturnbecausemoneycanbeusedtobuygoodsandservices.•Theopportunitycostofholdingmoneyistheinterestthatcouldbeearnedoninterest-earningassets.•Anincreaseintheinterestrateraisestheopportunitycostofholdingmoney.Asaresult,thequantityofmoneydemandedisreduced.•EquilibriumintheMoneyMarket–Accordingtothetheoryofliquiditypreference:•Theinterestrateadjuststobalancethesupplyanddemandformoney.•Thereisoneinterestrate,calledtheequilibriuminterestrate,atwhichthequantityofmoneydemandedequalsthequantityofmoneysupplied.•EquilibriumintheMoneyMarket–Assumethefollowingabouttheeconomy:•Thepricelevelisstuckatsomelevel.•Foranygivenpricelevel,theinterestrateadjuststobalancethesupplyanddemandformoney.•Thelevelofoutputrespondstotheaggregatedemandforgoodsandservices.Figure1EquilibriumintheMoneyMarketQuantityofMoneyInterestRate0MoneydemandQuantityfixedbytheFedMoneysupplyr2M2dMdr1EquilibriuminterestrateCopyright©2004South-WesternTheDownwardSlopeoftheAggregateDemandCurve•Thepricelevelisonedeterminantofthequantityofmoneydemanded.•Ahigherpricelevelincreas