布兰查得 宏观经济 课件 第5章

彭更问曰：“後车数十乘，从者数百人，以传食於诸侯，不以泰乎？”（泰，甚也）孟子曰：“非其道，则一箪食不可受於人。如其道，则舜受尧之天下，不觉得泰。子觉得泰乎？”曰：“否！士无事而食，不可也。”曰：“子不通功易事（事与功者，盖所作未成，则谓之事；事之成，则谓之功）

，以羡（馀也）补不足，则农有馀粟，女有馀布。子如通之，则梓、匠、轮、舆，皆得食於子。凡人当通功易事，乃可各以奉其用。於此有人焉，入则孝，出则悌，守先王之道，以待後之学者，而不得食於子。子何尊梓、匠、轮、舆而轻为仁义者哉？”曰：“梓、匠、轮、舆，其志将以求食也。君子之为道也，其志亦将以求食与？”曰：“子何以其志为哉？其有功於子，可食而食之矣。且子食志乎，食功乎？”曰：“食志。”曰：“有人於此，毁瓦画墁，其志将以求食也，则子食之乎？”曰：“否。”曰：“然则子非食志也，食功也。”

——孟子，滕文公章句下

2TheGoodsMarket

andtheISRelationEquilibriuminthegoodsmarketexistswhenproduction,Y,isequaltothedemandforgoods,Z.ThisconditioniscalledtheISrelation.Inthesimplemodeldevelopedinchapter3,weassumeinvestmentwasconstant,andtheinterestratedidnotaffectthedemandforgoods.Theequilibriumconditionwasgivenby:5-13Investment,Sales,

andtheInterestRateInfact,investmentisfarfromconstant.Inthischapter,wecapturetheeffectsoftwofactorsaffectinginvestment:Thelevelofsales(+)Theinterestrate(-)4DeterminingOutputTakingintoaccounttheinvestmentrelationabove,theequilibriumconditioninthegoodsmarketbecomes:Production(theleftsideoftheequation)mustbeequaltothedemandforgoods(therightside).

5DeterminingOutputForagivenvalueoftheinterestratei,demandisanincreasingfunctionofoutput(fromoutputtodemand),fortworeasons:Anincreaseinoutputleadstoanincreaseinincomeandalsotoanincreaseindisposableincome.Anincreaseinoutputalsoleadstoanincreaseininvestment.Therelationbetweendemandandoutput,foragiveninterestrate,isrepresentedbytheupward-slopingcurveZZ.6TheDeterminationofOutputThedemandforgoodsisanincreasingfunctionofoutput.Equilibriumrequiresthatthedemandforgoodsbeequaltooutput.EquilibriumintheGoodsMarketFigure5-17TheDeterminationofOutputNotetwocharacteristicsofZZ:BecausewehavenotassumedthattheconsumptionandinvestmentrelationsinEquation(5.2)arelinear,ZZis,ingeneral,acurveratherthanaline.ZZisdrawnflatterthana45-degreelinebecauseit’sassumedthatanincreaseinoutputleadstoalessthanone-for-oneincreaseindemand（Intheory，thesumoftheincreaseinconsumptionandinvestmentbothcouldexceedtheinitialincreaseinoutput）.Figure5-18DerivingtheISCurveAtanylevelofoutput(giventheoutput),thehigherinterestrateimplieddecreaseininvestment.Anincreaseintheinterestratedecreasesthedemandforgoodsatanylevelofoutput.TheEffectsofanIncreasein

theInterestRateonOutputFigure5-29Thetransmissionmechanism(传导机制)ofFigure5-2canbereasoninwords:step1:Anincreaseintheinterestrateleadstoandecreaseininvestment.Step2:Thedecreaseininvestmentleadstoadecreaseinoutput,stpe3:Thedecreaseinoutputfurtherdecreaseconsumptionandinvestment.Inotherwords,theinitialdecreaseininvestmentleadstoalargerdecreaseinoutputthroughthemultipliereffect(乘数效应).10DerivingtheISCurveUsingfigure5-2,wecanfindtheequilibriumvalueofoutputisassociatedwithanyvalueofinterestrate.Equilibriuminthegoodsmarketimpliesthatanincreaseintheinterestrateleadstoadecreaseinoutput.TheIScurveisdownwardsloping.TheDerivationoftheISCurveFigure5-311DerivingtheISCurveUsingFigure5-3,wecanfindtherelationbetweenequilibriumoutputandtheinterestrate.Panel5-3(a)reproducesFigure5-2.TheinterestrateiimpliesalevelofoutputequaltoY.Panel5-3(b)plotsequilibriumoutputYonthehorizontalaxisagainsttheinterestrateontheverticalaxis.Thisrelationbetweentheinterestrateandoutputisrepresentedbythedownward–slopingcurve,orIScurve（IS曲线）(frominterestratetooutput)。.12DerivingtheISCurveGiventheinterestrateshiftchangesinfactorsthatdecrease(increase)thedemandforgoods,shifttheIScurvetotheleft(right).

ShiftsoftheISCurveFigure5-413ShiftsoftheISCurveLet’ssummarize:Equilibriuminthegoodsmarketimpliesthatanincreaseintheinterestrateleadstoadecreaseinoutput.Giventheinterestrate,changesinfactorsthatdecreasethedemandforgoods,shifttheIScurvetotheleft.14FinancialMarkets

andtheLMRelationTheinterestrateisdeterminedbytheequalityofthesupplyofandthedemandformoney:M

=nominalmoneystock

$YL(i)=demandformoney

$Y=nominalincome

i=nominalinterestrate5-215RealMoney,RealIncome,

andtheInterestRateTheLMrelation（LM关系）:Inequilibrium,thereal

moneysupply（真实货币供给）—thatis,themoneystockintermsof

goods,notdollar—mustbeequaltotherealmoneydemand,whichdependsonrealincome,Y,andtheinterestrate,i:Fromchapter2,recallthatNominalGDP=RealGDPmultipliedbytheGDPdeflator:Equivalently:16DerivingtheLMCurveForagivenlevelofrealincome,Y,realmoneydemandisadecreasingfunction（减函数）

oftheinterestrate.Anincreaseinincomeleads,atagiveninterestrate,toanincreaseinthedemandformoney.Giventhemoneysupply,thisleadstoanincreaseintheequilibriuminterestrate.TheEffectsofanIncreaseinIncomeontheInterestRateFigure5-517DerivingtheLMCurveEquilibriuminfinancialmarketsimpliesthatanincreaseinincomeleadstoanincreaseintheinterestrate.TheLMcurveisupward-sloping.Aseconomistssaying:“highereconomicactivityputspressureoninterestrate.”TheDerivationoftheLMCurveFigure5-618DerivingtheLMCurveFromFigure5-6welearn:Panel5-6(a)reproducesFigure5-5Panel5-6(b)plotstheequilibriuminterestrateiontheverticalaxisagainstincomeonthehorizontalaxisThisrelationbetweenoutputandtheinterestrateisrepresentedbytheupward-slopingcurveinPanel5-6(b).ThiscurveiscalledtheLMcurve(LM曲线).(fromoutputtointerestrate)19ShiftsoftheLMCurveAtanylevelofrealincome,adecrease(increase)intherealmoneysupplyleadstoanincrease(decrease)intheinterestrate,itleadstheLMcurveshiftup.ShiftsoftheLMCurveFigure5-720ShiftsoftheLMCurveLet’ssummarize:Equilibriuminfinancialmarketsimpliesthat,foragivenrealmoneysupply,anincreaseinthelevelofincome,whichincreasesthedemandformoney,leadstoanincreaseintheinterestrate.AnincreaseinthemoneysupplyshiftstheLMcurvedown;adecreaseinthemoneysupplyshiftstheLMcurveup.21PuttingtheISandthe

LMRelationsTogetherEquilibriuminthegoodsmarketimpliesthatanincreaseintheinterestrateleadstoadecreaseinoutput.Equilibriuminfinancialmarketsimpliesthatanincreaseinoutputleadstoanincreaseintheinterestrate.WhentheIScurveintersectstheLMcurve,bothgoodsandfinancialmarketsareinequilibrium.thisfigureholdstheanswertomanyquestionsinmacroeconomics.TheIS-LMModel5-3Figure5-822FiscalPolicy,Activity,

andtheInterestRateFiscalcontraction,orfiscalconsolidation,referstofiscalpolicythatreducesthebudgetdeficit.Anincreaseinthedeficitiscalledafiscalexpansion.TaxesaffecttheIScurve,nottheLMcurve.23

皇佑二年，吴中大饥，殍殣枕路，是时范文正领浙西，发粟及募民存饷，为术甚备，吴人喜竞渡，好为佛事。希文乃纵民竞渡，太守日出宴于湖上，自春至夏，居民空巷出游。又召诸佛寺主首，谕之曰：“饥歳工价至贱，能够大兴土木之役。”于是诸寺工作鼎兴。又新敖仓吏舍，日役千夫。监司奏劾杭州不恤荒政，嬉游不节，及公私兴造，伤耗民力，文正乃自条叙所以宴游及兴造，皆欲以发有馀之财，以惠贫者。贸易饮食、工技服力之人，仰食于公私者，日无虑数万人。荒政之施，莫此为大。是歳，两浙唯杭州晏然，民不流徙，皆文正之惠也。岁饥发司农之粟，募民兴利，近岁遂著为令。既已恤饥，因之以成就民利，此先王之美泽也。

———沈括，梦溪笔谈24管子曰：“难过者不能够致功，故尝至味而罢至乐，而雕卵然后瀹之，雕撩然后爨之。丹砂之穴不塞，则商贾不处。富者靡之，贫者为之。此百姓之怠生，百振而食，非独自为也，为之畜化用。”（管子，奢靡篇）

（译文：心灵受到残害旳人不能期望会立下功德，此所以人们应被允许餍食山珍海味，享有柔关音乐，把彩蛋放在雕花木所升旳火上烹煮。只要朱砂矿不被封闭，商人是不愿枯坐家中而会到处活动旳。让富人穷奢极侈，(这么)穷人就有工作做了。此为平民谋生与不必仰赖救济就能够维生旳道理。。这不是他们所能独自办到旳，而是有人用钱赡养他们。）25FiscalPolicy,Activity,

andtheInterestRateTheEffectsofanIncreaseinTaxesAnincreaseintaxesshiftstheIScurvetotheleft,andleadstoadecreaseintheequilibriumlevelofoutputandtheequilibriuminterestrate.Figure5-926Inwords:

Theincreaseintaxesleadstolowerdisposableincome,whichcausespeopletodecreasetheirconsumption.

Theresultthroughthemultipliereffectisadecreaseinoutputandincome.thedecreaseinincomereducesthedemandformoney,leadingtoadecreaseintheinterestrate.Thedeclineintheinterestratereducesbutdoesnotcompletelyoffsettheeffectofhighertaxesonthedemandforgoods.

27

DeficitReduction:GoodorBadforInvestment?Investment=Privatesaving+Publicsaving

I=S+(T–G)Afiscalcontractionmaydecreaseinvestment.Or,lookingatthereversepolicy,afiscalexpansion—adecreaseintaxesoranincreaseinspending—mayactuallyincreaseinvestment.Becauseinvestmentdependsonboththeinterestrateandonsales,sowecannotdeterminewhatchangehappedtoinvestment?28MonetaryPolicy,Activity,

andtheInterestRateMonetarycontraction,ormonetarytightening,referstoadecreaseinthemoneysupply.Anincreaseinthemoneysupplyiscalledmonetaryexpansion.MonetarypolicydoesnotaffecttheIScurve,onlytheLMcurve.Forexample,anincreaseinthemoneysupplyshiftstheLMcurvedown.

29MonetaryPolicy,Activity,

andtheInterestRateMonetaryexpansionleadstohigheroutputandalowerinterestrate.TheEffectsofaMonetaryExpansionFigure5-1030Inwords:

Theincreaseinmoneyleadstoalowerinterestrate.thelowerinterestrateleadstoanincreaseininvestmentand,which,throughthemultipliereffect,leadstoanincreaseindemandandoutput.31UsingaPolicyMixThecombinationofmonetaryandfiscalpolicesisknownasthemonetary-fiscalpolicymix,orsimply,thepolicymix.Table5-1TheEffectsofFiscalandMonetaryPolicy.

ShiftofISShiftofLMMovementofOutputMovementinInterestRateIncreaseintaxesleftnonedowndownDecreaseintaxesrightnoneupupIncreaseinspendingrightnoneupupDecreaseinspendingleftnonedowndownIncreaseinmoneynonedownupdownDecreaseinmoneynoneupdownup5-432TheU.S.Recessionof2023Figure1TheU.S.GrowthRate,1999:1-2023:433

TheU.S.Recessionof2023Figure2TheFederalFundsRate,1999:1-2023:434

TheU.S.Recessionof2023Figure3U.S.FederalGovernmentRevenuesandSpending(asratiostoGDP),1999:1-2023:435

TheU.S.Recessionof2023Figure4TheU.S.Recessionof202336

TheU.S.Recessionof2023Whathappenedin2023wasthefollowing:ThedecreaseininvestmentdemandledtoasharpshiftoftheIScurvetotheleft,fromIStoIS’.TheincreaseinthemoneysupplyledtoadownwardshiftoftheLMcurve,fromLMtoLM’.ThedecreaseintaxratesandtheincreaseinspendingbothledtoashiftoftheIScurvetotheright,fromIS’’toIS’.37HowdoestheIS-LM

ModelFittheFacts?Introducingdynamicsformallywouldbedifficult,butwecandescribethebasicmechanismsinwords.Consumersarelikelytotakesometimetoadjusttheirconsumptionfollowingachangeindisposableincome.Firmsarelikelytotakesometimetoadjustinvestmentspendingfollowingachangeintheirsale