宏观经济学PPT课件

TheClassicalLong-RunModel,.,2,TheClassicalLong-RunModel,EconomistssometimesdisagreewitheachotherActuallymuchmoreagreementexistsamongeconomiststhanthereappearstobeOncedistinctionbetweenlong-runandshort-runbecomesclearManyapparentdisagreementsamongmacroeconomistsdissolveIfnotimehorizonisspecified,however,aneconomistislikelytofocusonhorizonheorshefeelsismostimportantSomethingaboutwhicheconomistssometimesdodisagree,.,3,TheClassicalLong-RunModel,Ideally,wewouldlikeoureconomytodowellinbothlong-runandshort-runUnfortunately,thereisoftenatrade-offbetweenthesetwogoalsDoingbetterinshort-runcanrequiresomesacrificeoflong-rungoals,andviceversaPolicesthatcanhelpussmoothouteconomicfluctuationsmayproveharmfultogrowthinthelong-runWhilepoliciesthatpromiseahighrateofgrowthmightrequireustoputupwithmoreseverefluctuationsinshort-run,.,4,MacroeconomicModels:ClassicalVersesKeynesian,Classicalmodel,developedbyeconomistsin19thandearly20thcenturies,wasanattempttoexplainakeyobservationabouteconomyOverperiodsofseveralyearsorlonger,economyperformsratherwellIfwethinkintermsofdecadesratherthanyearsorquarters,businesscyclefadesinsignificanceIntheclassicalview,thisbehaviorisnoaccidentPowerfulforcesareatworkthatdriveeconomytowardsfullemploymentAnimportantgroupofmacroeconomistscontinuestobelievethatclassicalmodelisusefuleveninshorterrunIn1936,inmidstofGreatDepression,BritisheconomistJohnMaynardKeynesofferedanexplanationforeconomyspoorperformanceArguedthat,whileclassicalmodelmightexplaineconomysoperationinlong-run,long-runcouldbeaverylongtimeinarriving,.,5,MacroeconomicModels:ClassicalVersesKeynesian,Keynesianideasbecameincreasinglypopularinuniversitiesandgovernmentagenciesduring1940sand1950sBymid-1960s,entireprofessionhadbeenwonoverMacroeconomicswasKeynesianeconomicsClassicalmodelwasremovedfromvirtuallyallintroductoryeconomicstextbooksClassicalmodelisstillimportantInrecentdecadestherehasbeenanactivecounterrevolutionagainstKeynessapproachtounderstandingthemacroeconomyUsefulinunderstandingeconomyoverlong-runWhileKeynessideasandtheirfurtherdevelopmenthelpusunderstandeconomicfluctuationsmovementsinoutputarounditslong-runtrendClassicalmodelhasprovenmoreusefulinexplainingthelong-runtrenditself,.,6,AssumptionsoftheClassicalModel,AllmodelsbeginwithassumptionsabouttheworldClassicalmodelisnoexceptionManyofitsassumptionsaresimplifyingMakemodelmoremanageable,enablingustoseethebroadoutlinesofeconomicbehaviorwithoutgettinglostindetailsOneassumptioninclassicalviewthatgoesbeyondmeresimplificationMarketsclearPriceineverymarketwilladjustuntilquantitysuppliedandquantitydemandedareequal,.,7,AssumptionsoftheClassicalModel,Market-clearingassumptionprovideshintaboutwhyclassicalmodeldoesabetterjoboverlongertimeperiods(severalyearsormore)thanshorteronesWelluseclassicalmodeltoansweravarietyofimportantquestionsabouteconomyinlong-run,suchasHowistotalemploymentdetermined?Howmuchoutputwillweproduce?Whatroledoestotalspendingplayintheeconomy?Whathappenswhenthingschange?,.,8,HowMuchOutputWillWeProduce?,Howcanwedisentanglewebofeconomicinteractionsweseearoundus?Decidewhichmarketormarketsbestsuittheproblembeinganalyzed,andIdentifybuyersandsellersIdentifytypeofenvironmentinwhichtheytradeButwhichmarketshouldwestartwith?LogicalstartismarketforresourcesLabor,landandnaturalresources,capitalandentrepreneurshipWellconcentrateourattentiononlaborOurquestionisHowmanyworkerswillbeemployedintheeconomy?,.,9,Figure1:TheLaborMarket,.,10,TheLaborMarket,LaborsupplycurveslopesupwardBecauseaswagerateincreasesmoreandmoreindividualsarebetteroffworkingthannotworkingThus,ariseinwagerateincreasesnumberofpeoplewhowanttoworktosupplytheirlaborAswagerateincreaseseachfirmwillfindthattomaximizeprofititshouldemployfewerworkersthanbeforeWhenallfirmsbehavethiswaytogetherariseinwageratewilldecreasequantityoflabordemandedThisiswhyeconomyslabordemandcurveslopesdownwardInclassicalview,economyachievesfullemploymentonitsown,.,11,DeterminingtheEconomysOutput,Mosteffectivewaytomasteramacroeconomicmodelis“divideandconquer”Startwithpartofmodel,understanditwell,andthenaddinotherpartsAccordingly,ourclassicalanalysisofeconomyisdividedintotwoseparatequestionsWhatwouldbethelong-runequilibriumoftheeconomyiftherewereaconstantstateoftechnologyAndifquantitiesofallresourcesbesideslaborwerefixed?Whathappenstothislong-runequilibriumwhentechnologyandquantitiesofotherresourceschange?,.,12,TheProductionFunction,RelationshipbetweentotalemploymentandtotalproductionintheeconomyGivenbyeconomysaggregateproductionfunctionShowstotaloutputeconomycanproducewithdifferentquantitiesoflaborGivenconstantamountsofotherresourcesandcurrentstateoftechnologyInclassical,long-runvieweconomyreachesitspotentialoutputautomaticallyAnimportantconclusionofclassicalmodelandanimportantcharacteristicoftheeconomyinlong-runOutputtendstowarditspotential,full-employmentlevelonitsown,withnoneedforgovernmenttosteertheeconomytowardit,.,13,Figure2:OutputDeterminationintheClassicalModel,.,14,TheRoleofSpending,Whatifbusinessfirmsareunabletosellalloutputproducedbyafullyemployedlaborforce?EconomywouldnotbeabletosustainfullemploymentforverylongIfweareassertingthatpotentialoutputisanequilibriumfortheeconomyHadbetterbesurethattotalspendingonoutputisequaltototalproductionduringtheyearButcanwebesureofthis?Inclassicalviewanswerisyes,.,15,TotalSpendinginaVerySimpleEconomy,ImagineaworldwithjusttwotypesofeconomicunitsHouseholdsandbusinessfirmsCircularFlowAdiagramthatshowshowgoods,resources,anddollarpaymentsflowbetweenhouseholdsandfirmsInasimpleeconomywithjusthouseholdsandfirmsinwhichhouseholdsspendalloftheirincomeTotalspendingmustbeequaltototaloutputKnownasSaysLaw,.,16,Figure3:TheCircularFlow,.,17,TotalSpendinginaVerySimpleEconomy,SaysLawnamedafterclassicaleconomistJeanBaptisteSay(1767-1832),whopopularizedtheideaInSaysownwords“Aproductisnosoonercreatedthanit,fromthatinstant,affordsamarketforotherproductstothefullextentofitsownvalueThus,themerecircumstanceofthecreationofoneproductimmediatelyopensaventforotherproducts”SayslawstatesthatbyproducinggoodsandservicesFirmscreateatotaldemandforgoodsandservicesequaltowhattheyhaveproducedorSupplycreatesitsowndemand,.,18,TotalSpendinginaMoreRealisticEconomy,DoesSayslawalsoapplyinamorerealisticeconomy?IntherealworldHouseholdsdontspendalltheirincomeRather,someoftheirincomeissavedorgoestopaytaxesHouseholdsarenottheonlyspendersintheeconomyBusinessesandgovernmentbuysomeofthefinalgoodsandservicesweproduceInadditiontomarketsforgoodsandresources,thereisalsoaloanablefundsmarketWherehouseholdsavingismadeavailabletoborrowersinbusinessorgovernmentsectors,.,19,SomeNewMacroeconomicVariables,Plannedinvestmentspending(IP)overaperiodoftimeistotalinvestmentspending(I)minuschangeininventoriesovertheperiodIP=IinventoriesNettaxes(T)aretotalgovernmenttaxrevenueminusgovernmenttransferpaymentsT=totaltaxrevenuetransfersHouseholdsaving(S)ItsoftenusefultoarriveathouseholdsavingintwostepsDeterminehowmuchincomehouseholdsectorhasleftafterpaymentofnettaxesHouseholdsectorsdisposableincomeDisposableIncome=TotalIncomeNetTaxesPartthatisnotspentisdefinedassaving(S)S=DisposableIncomeCTotalSpendinginClassicaInClassica,totalspendingissumofpurchasesmadebyhouseholdsector(C),businesssector(IP),andgovernmentsector(G)Totalspending=C+IP+G,.,20,SomeNewMacroeconomicVariables,SavingandnettaxesarecalledleakagesoutofspendingAmountofincomethathouseholdsreceive,butdonotspendTherearealsoinjectionsspendingfromsourcesotherthanhouseholdsAgovernmentspurchasesofgoodsandservicesPlannedinvestmentspending(IP)TotalspendingwillequaltotaloutputifandonlyiftotalleakagesintheeconomyareequaltototalinjectionsOnlyifsumofsavingandnettaxesisequaltosumofplannedinvestmentspendingandgovernmentpurchases,.,21,Figure4:LeakagesandInjections,.,22,TheLoanableFundsMarket,WherehouseholdsmaketheirsavingavailabletothosewhoneedadditionalfundsTotalsupplyofloanablefundsisequaltohouseholdsavingFundssuppliedareloanedout,andhouseholdsreceiveinterestpaymentsonthesefundsBusinessesdemandforloanablefundsisequaltotheirplannedinvestmentspendingFundsobtainedareborrowed,andfirmspayinterestontheirloansBudgetdeficitExcessofgovernmentpurchasesovernettaxesBudgetofsurplusExcessofnettaxesovergovernmentpurchasesWhengovernmentpurchasesofgoodsandservices(G)aregreaterthannettaxes(T)GovernmentrunsabudgetdeficitequaltoGTWhengovernmentpurchasesofgoodsandservices(G)arelessthannettaxes(T)GovernmentrunsabudgetsurplusequaltoT-G,.,23,TheSupplyofFundsCurve,SinceinterestisrewardforsavingandsupplyingfundstofinancialmarketRiseininterestrateincreasesquantityoffundssupplied(householdsaving),whileadropininterestratedecreasesitSupplyoffundscurveIndicateslevelofhouseholdsavingatvariousinterestratesQuantityoffundssuppliedtothefinancialmarketdependspositivelyoninterestrateThisiswhythesaving,orsupplyoffunds,curveslopesupwardOtherthingscanaffectsavingsbesidestheinterestrate,includingTaxratesExpectationsaboutthefutureGeneralwillingnessofhouseholdstopostponeconsumption,.,24,Figure5:SupplyofHouseholdLoanableFunds,.,25,TheDemandforFundsCurve,WheninterestratefallsinvestmentspendingandthebusinessborrowingneededtofinanceitriseBusinessdemandforfundscurveslopesdownwardWhataboutgovernmentsdemandforfunds?Willit,too,beinfluencedbytheinterestrate?ProbablynotverymuchGovernmentseemstobecushionedfromcost-benefitconsiderationsthathauntbusinessdecisionsAnycompanypresidentwhoignoredinterestratesindecidinghowmuchtoborrowwouldbequicklyoutofajobU.S.presidentsandlegislatorshaveoftendonesowithlittlepoliticalcostGovernmentsectorsdeficitanditsdemandforfundsareindependentofinterestrateAsinterestratedecreasesquantityoffundsdemandedbybusinessfirmsincreasesWhilequantitydemandedbygovernmentremainsunchangedTherefore,totalquantityoffundsdemandedrises,.,26,Figure6:BusinessDemandforLoanableFunds,.,27,Figure7:TheDemandforFunds,.,28,EquilibriumintheLoanableFundsMarket,InclassicalviewloanablefundsmarketisassumedtoclearInterestratewillriseorfalluntilquantitiesoffundssuppliedanddemandedareequalCanwebesurethatalloutputproducedatfullemploymentwillbepurchased?,.,29,Figure8:LoanableFundsMarketEquilibrium,.,30,TheLoanableFundsMarketandSaysLaw,Aslongasloanablefundsmarketclears,SayslawholdsTotalspendingequalstotaloutputThisistrueeveninamorerealisticeconomywithsaving,taxes,investmentandgovernmentdeficitHeresanotherwaytoseethesameresult,intermsofasimpleequationLoanablefundsmarketclearsS=IP+(GT)RearrangingthisequationbymovingTtoleftsideLoanablefundsmarketclearsS+T=IP+GSayslawshowsthattotalvalueofspendingineconomywillequaltotalvalueofoutputRulesoutageneraloverproductionorunderproductionofgoodsintheeconomyItdoesnotpromiseusthateachfirmwillbeabletosellalloftheparticulargooditproduces,.,31,Figure9:AnExpandedCircularFlow,.,32,TheClassicalModel:ASummary,BeganwithacriticalassumptionAllmarketsclearInclassicalmodel,governmentneedntworryaboutemploymentEconomywillachievefullemploymentonitsownInclassicalmodel,governmentneedntworryabouttotalspendingEconomywillgeneratejustenoughspendingonitsowntobuyoutputthatafullyemployedlaborforceproduces,.,33,UsingtheTheory:FiscalPolicyintheClassicalModel,Couldgovernmentincreaseeconomystotalemploymentandtotaloutputbyraisingtotalspending?TwoideasforincreasingspendingcometomindGovernmentcouldsimplypurchasemoreoutputitselfMoregoods,liketanksandpolicecars,ormoreservices,likethoseprovidedbyhighschoolteachersandjudgesGovernmentcouldcutnettaxes,lettinghouseholdskeepmoreoftheirincomeSotheywouldspendmoreonfood,clothing,furniture,newcars,andsoonFiscalpolicyi