LikeanEconomist(宏观经济学-加州大学-詹姆斯·布

Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-1,CHAPTER3,ThinkingLikeanEconomist,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-2,Questions,Iseconomicsascience?Whatdoeconomistsmeanbyamodel?Whydoeconomistsusemathematicalmodelssomuch?Whatpatternsandhabitsofthoughtmustyoulearntosuccessfullythinklikeaneconomist?,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-3,Economics,isasocialsciencefocusesonhumanbeingsandhowtheybehavedebateswithineconomicslastlongerthanthoseinnaturalscienceslesslikelytoendinconsensuseconomistsareunabletoundertakelarge-scaleexperimentsthesubjectsstudiedbyeconomists-people-havemindsoftheirownexpectationsofthefutureplayanimportantrole,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-4,TheImportanceofExpectations:AnExample,Thestockmarketcrashof1929changedwhatAmericansexpectedaboutthefutureoftheeconomy,Expectationsthatfutureincomewouldbelowerbecamerealized,spending,production,layoffs,income,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-5,Figure3.1-TheStockMarket,1928-1932,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-6,Economics,isaquantitativescienceusesarithmetictomeasureeconomicvariablesofinterestusesmathematicalmodelstorelateeconomicvariablesofinterestinvolvesaparticularwayofthinkingabouttheworldusinguniquetechnicallanguageaspecificsetofdata,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-7,Economists,useaspecialsetofanalogiesandmetaphorstodescribethefunctioningofthemacroeconomycurves“shift”moneyhasa“velocity”thecentralbank“pushestheeconomyupthePhillipscurve”,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-8,Figure3.2-PushingtheEconomyUpthePhillipsCurve,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-9,DominantConcepts,theimageofthe“circularflowofeconomicactivity”theuseoftheword“market”theideaof“equilibrium”useofgraphsanddiagramsequationsdepictedbygeometriccurvessituationsofequilibriumoccurwherecurvescrosschangesineconomydemonstratedbyshiftsinthecurves,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-10,TheCircularFlow,patternsofspending,income,andproductionflowingthroughtheeconomyflowofpurchasingpower,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-11,TheCircularFlow,“incomeside”firmsbuythefactorsofproductionfromhouseholdsmoneypaymentsflowfromfirmstohouseholds“expenditureside”householdsbuygoodsandservicesfromfirmsmoneypaymentsflowfromhouseholdstofirms,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-12,Figure3.3-TheCircularFlowDiagram,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-13,CircularFlow,canbemadetobemorerealisticbyaddingthegovernmentfinancialmarketsinternationaltradeandfinance,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-14,Figure3.4-TheCircularFlowofEconomicActivity,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-15,DifferentMeasuresoftheCircularFlow,“expenditureside”measureconsumptioninvestmentgovernmentpurchasesnetexports“incomeside”measurepurchasesoflabor,capital,andnaturalresourcesowneddirectlyorindirectlybyhouseholds,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-16,DifferentMeasuresoftheCircularFlow,“usesofincome”measurewherehouseholdsdecidetousetheirincomesavingtaxesconsumption,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-17,Markets,areusedasametaphorforthecomplexprocessesofmatchingandexchangethattakeplaceintheeconomyeconomistsassumethatbuyersandsellersarewell-informedaboutprevailingpricesandquantities,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-18,Equilibrium,isapoint(orpoints)ofbalanceatwhichsomeeconomicquantityisneitherrisingnorfallingonceequilibriumisidentified,economistscandeterminehowfasteconomicforceswillpushtheeconomytothepointsofequilibrium,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-19,GraphsandEquations,analgebraicequationrelatingtwovariablescanalsoberepresentedasacurvedrawnonagraphthesolutiontoasetoftwoequationsisthepointonagraphwherethetwocurvesthatrepresenttheequationsintersect,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-20,Figure3.5-TwoFormsoftheProductionFunction,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-21,UsingGraphsInsteadofEquations,behavioralrelationshipsbecomecurvesthatshiftaroundonagraphconditionsofeconomicequilibriumcanberepresentedbythepointswherethecurvesdescribingbehavioralrelationshipsintersect,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-22,UsingGraphsInsteadofEquations,changesinthestateoftheeconomycanbeshownasmovementsintheintersectionofthecurves,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-23,BuildingModels,restricttheproblemtoonlyafewbehavioralrelationshipsandequilibriumconditionscapturetheserelationshipsandequilibriumconditionsinsimplealgebraicequationsusediagramstorepresenttheequationsapplythemodeltotherealworld,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-24,ImportantConceptsinMacroeonomicModels,representativeagentsassumethatallparticipantsintheeconomyarethesameexaminethedecision-makingofoneindividualandthengeneralizetotheeconomyasawhole,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-25,ImportantConceptsinMacroeonomicModels,opportunitycostsoccurwhenanydecisionismademeasuredbythevalueofthebestalternativeforegone,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-26,ImportantConceptsinMacroeonomicModels,expectationformationmacroeconomicmodelsmustexplaintheamountoftimepeoplespendthinkingaboutthefuturetheinformationthatpeoplehaveavailabletherulesofthumbusedtoturninformationintoexpectations,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-27,ImportantConceptsinMacroeonomicModels,expectationformationstaticexpectationsdecisionmakersdonotthinkaboutthefutureadaptiveexpectationsdecisionmakersassumethatthefutureisgoingtobeliketherecentpast,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-28,ImportantConceptsinMacroeonomicModels,expectationformationrationalexpectationsdecisionmakersspendasmuchtimeastheycanthinkingaboutthefutureandknowasmuchaboutthestructureandbehavioroftheeconomyasthemodelbuilderdoes,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-29,BuildingandSolvinganEconomicModel,writeequationsthatrepresentbehavioralrelationshipsstatehowthe“effects”arerelatedtothe“causes”drawadiagramtohelpvisualizetherelationshipconsiderequilibriumconditionscanbeshownasintersectionsondiagram,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-30,BuildingandSolvinganEconomicModel:AnExample,Theproductionfunctionrelatestheeconomyscapital-laborratio(K/L)theleveloftechnologyorefficiencyofthelaborforce(E)thelevelofrealGDPperworker(Y/L),Cobb-Douglasproductionfunction,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-31,BuildingandSolvinganEconomicModel:AnExample,Equilibriumconditionforbalancedgrowththeratiooftheeconomyscapitalstock(K)toitslevelofoutput(Y)mustbeconstant,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-32,BuildingandSolvinganEconomicModel:AnExample,Equilibriumconditionforbalancedgrowth,s=shareoftotalincomeintheeconomysavedandinvestedn=proportionalgrowthrateofthelaborforceg=proportionalgrowthrateoftheefficiencyofthelaborforce=thedepreciationrate,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-33,BuildingandSolvinganEconomicModel:AnExample,arithmeticcanbeusedtodeterminethesteady-stateoutputperworker,LetE=$10,000,=1/2,s=25%,n=1%,g=1%,and=3%.,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-34,BuildingandSolvinganEconomicModel:AnExample,sinceK/Y=5,thismustimplythatK/L=5Y/LsubstitutingforandEtintheCobb-Douglasproductionfunction,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-35,BuildingandSolvinganEconomicModel:AnExample,inequilibrium,bothconditionsmusthold,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-36,BuildingandSolvinganEconomicModel:AnExample,algebracanbeusedtodeterminethesteady-stateoutputperworker,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-37,BuildingandSolvinganEconomicModel:AnExample,puttinginthebalanced-growthcondition,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-38,BuildingandSolvinganEconomicModel:AnExample,LetE=$10,000,=1/2,s=25%,n=1%,g=1%,and=3%,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-39,BuildingandSolvinganEconomicModel:AnExample,graphscanalsobeusedtoshowthesteady-stateoutputperworkertheproductionfunctioncanbedrawnwithoutputperworker(Y/L)ontheverticalaxisandcapitalperworker(K/L)onthehorizontalaxistheequilibriumconditionforbalancedgrowthcanalsobeshownK/L=s/(n+g+),Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-40,Figure3.6-EquilibriumOutputperWorker,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-41,TheAdvantagesofUsingAlgebra,bestwaytosummarizecause-and-effectbehavioralrelationshipsallowsustoconsiderdifferentpossiblesystematicrelationshipsbychangingthevalueofparameters,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-42,Figure3.7-ASingleEquation,aHostofRelationships,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-43,Figure3.8-ChangingParameterValuesandtheShapeoftheCobb-DouglasProductionFunction,Copyright2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.,3-