LikeanEconomist宏观经济学加州大学詹姆斯·布讲义

QuestionsIseconomicsascience?Whatdoeconomistsmeanbyamodel?Whydoeconomistsusemathematicalmodelssomuch?Whatpatternsandhabitsofthoughtmustyoulearntosuccessfullythinklikeaneconomist?1Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.QuestionsIseconomicsascienc1Economicsisasocialsciencefocusesonhumanbeingsandhowtheybehavedebateswithineconomicslastlongerthanthoseinnaturalscienceslesslikelytoendinconsensuseconomistsareunabletoundertakelarge-scaleexperimentsthesubjectsstudiedbyeconomists--people--havemindsoftheirownexpectationsofthefutureplayanimportantrole2Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Economicsisasocialscience2C2TheImportanceofExpectations:AnExampleThestockmarketcrashof1929changedwhatAmericansexpectedaboutthefutureoftheeconomyExpectationsthatfutureincomewouldbelowerbecamerealizedspendingproductionlayoffsincome3Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.TheImportanceofExpectations3Figure3.1-TheStockMarket,1928-19324Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure3.1-TheStockMarket,4Economicsisaquantitativescienceusesarithmetictomeasureeconomicvariablesofinterestusesmathematicalmodelstorelateeconomicvariablesofinterestinvolvesaparticularwayofthinkingabouttheworldusinguniquetechnicallanguageaspecificsetofdata5Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Economicsisaquantitativesci5Economistsuseaspecialsetofanalogiesandmetaphorstodescribethefunctioningofthemacroeconomycurves“shift”moneyhasa“velocity”thecentralbank“pushestheeconomyupthePhillipscurve”6Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Economistsuseaspecialsetof6Figure3.2-PushingtheEconomyUpthePhillipsCurve7Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure3.2-PushingtheEcono7DominantConceptstheimageofthe“circularflowofeconomicactivity”theuseoftheword“market”theideaof“equilibrium”useofgraphsanddiagramsequationsdepictedbygeometriccurvessituationsofequilibriumoccurwherecurvescrosschangesineconomydemonstratedbyshiftsinthecurves8Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.DominantConceptstheimageof8TheCircularFlowpatternsofspending,income,andproductionflowingthroughtheeconomyflowofpurchasingpower9Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.TheCircularFlowpatternsofs9TheCircularFlow“incomeside”firmsbuythefactorsofproductionfromhouseholdsmoneypaymentsflowfromfirmstohouseholds“expenditureside”householdsbuygoodsandservicesfromfirmsmoneypaymentsflowfromhouseholdstofirms10Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.TheCircularFlow“incomeside”10Figure3.3-TheCircularFlowDiagram11Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure3.3-TheCircularFlow11CircularFlowcanbemadetobemorerealisticbyaddingthegovernmentfinancialmarketsinternationaltradeandfinance12Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.CircularFlowcanbemadetobe12Figure3.4-TheCircularFlowof

EconomicActivity13Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure3.4-TheCircularFlow13DifferentMeasuresoftheCircularFlow“expenditureside”measureconsumptioninvestmentgovernmentpurchasesnetexports“incomeside”measurepurchasesoflabor,capital,andnaturalresourcesowneddirectlyorindirectlybyhouseholds14Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.DifferentMeasuresoftheCirc14DifferentMeasuresoftheCircularFlow“usesofincome”measurewherehouseholdsdecidetousetheirincomesavingtaxesconsumption15Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.DifferentMeasuresoftheCirc15Marketsareusedasametaphorforthecomplexprocessesofmatchingandexchangethattakeplaceintheeconomyeconomistsassumethatbuyersandsellersarewell-informedaboutprevailingpricesandquantities16Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Marketsareusedasametaphor16Equilibriumisapoint(orpoints)ofbalanceatwhichsomeeconomicquantityisneitherrisingnorfallingonceequilibriumisidentified,economistscandeterminehowfasteconomicforceswillpushtheeconomytothepointsofequilibrium17Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Equilibriumisapoint(orpoin17GraphsandEquationsanalgebraicequationrelatingtwovariablescanalsoberepresentedasacurvedrawnonagraphthesolutiontoasetoftwoequationsisthepointonagraphwherethetwocurvesthatrepresenttheequationsintersect18Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.GraphsandEquationsanalgebra18Figure3.5-TwoFormsoftheProductionFunction19Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure3.5-TwoFormsofthe19UsingGraphsInsteadofEquationsbehavioralrelationshipsbecomecurvesthatshiftaroundonagraphconditionsofeconomicequilibriumcanberepresentedbythepointswherethecurvesdescribingbehavioralrelationshipsintersect20Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.UsingGraphsInsteadofEquati20UsingGraphsInsteadofEquationschangesinthestateoftheeconomycanbeshownasmovementsintheintersectionofthecurves21Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.UsingGraphsInsteadofEquati21BuildingModelsrestricttheproblemtoonlyafewbehavioralrelationshipsandequilibriumconditionscapturetheserelationshipsandequilibriumconditionsinsimplealgebraicequationsusediagramstorepresenttheequationsapplythemodeltotherealworld22Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingModelsrestrictthepr22ImportantConceptsinMacroeonomicModelsrepresentativeagentsassumethatallparticipantsintheeconomyarethesameexaminethedecision-makingofoneindividualandthengeneralizetotheeconomyasawhole23Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ImportantConceptsinMacroeon23ImportantConceptsinMacroeonomicModelsopportunitycostsoccurwhenanydecisionismademeasuredbythevalueofthebestalternativeforegone24Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ImportantConceptsinMacroeon24ImportantConceptsinMacroeonomicModelsexpectationformationmacroeconomicmodelsmustexplaintheamountoftimepeoplespendthinkingaboutthefuturetheinformationthatpeoplehaveavailabletherulesofthumbusedtoturninformationintoexpectations25Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ImportantConceptsinMacroeon25ImportantConceptsinMacroeonomicModelsexpectationformationstaticexpectationsdecisionmakersdonotthinkaboutthefutureadaptiveexpectationsdecisionmakersassumethatthefutureisgoingtobeliketherecentpast26Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ImportantConceptsinMacroeon26ImportantConceptsinMacroeonomicModelsexpectationformationrationalexpectationsdecisionmakersspendasmuchtimeastheycanthinkingaboutthefutureandknowasmuchaboutthestructureandbehavioroftheeconomyasthemodelbuilderdoes27Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.ImportantConceptsinMacroeon27BuildingandSolvinganEconomicModelwriteequationsthatrepresentbehavioralrelationshipsstatehowthe“effects”arerelatedtothe“causes”drawadiagramtohelpvisualizetherelationshipconsiderequilibriumconditionscanbeshownasintersectionsondiagram28Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingandSolvinganEconom28BuildingandSolvinganEconomicModel:AnExampleTheproductionfunctionrelatestheeconomy’scapital-laborratio(K/L)theleveloftechnologyorefficiencyofthelaborforce(E)thelevelofrealGDPperworker(Y/L)Cobb-Douglasproductionfunction29Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingandSolvinganEconom29BuildingandSolvinganEconomicModel:AnExampleEquilibriumconditionforbalancedgrowththeratiooftheeconomy’scapitalstock(K)toitslevelofoutput(Y)mustbeconstant30Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingandSolvinganEconom30BuildingandSolvinganEconomicModel:AnExampleEquilibriumconditionforbalancedgrowths=shareoftotalincomeintheeconomysavedandinvestedn=proportionalgrowthrateofthelaborforceg=proportionalgrowthrateoftheefficiencyofthelaborforce=thedepreciationrate31Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingandSolvinganEconom31BuildingandSolvinganEconomicModel:AnExamplearithmeticcanbeusedtodeterminethesteady-stateoutputperworkerLetE=$10,000,=1/2,s=25%,n=1%,g=1%,and=3%.32Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingandSolvinganEconom32BuildingandSolvinganEconomicModel:AnExamplesinceK/Y=5,thismustimplythatK/L=5Y/LsubstitutingforandEtintheCobb-Douglasproductionfunction33Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingandSolvinganEconom33BuildingandSolvinganEconomicModel:AnExampleinequilibrium,bothconditionsmusthold34Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingandSolvinganEconom34BuildingandSolvinganEconomicModel:AnExamplealgebracanbeusedtodeterminethesteady-stateoutputperworker35Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingandSolvinganEconom35BuildingandSolvinganEconomicModel:AnExampleputtinginthebalanced-growthcondition36Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingandSolvinganEconom36BuildingandSolvinganEconomicModel:AnExampleLetE=$10,000,=1/2,s=25%,n=1%,g=1%,and=3%37Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingandSolvinganEconom37BuildingandSolvinganEconomicModel:AnExamplegraphscanalsobeusedtoshowthesteady-stateoutputperworkertheproductionfunctioncanbedrawnwithoutputperworker(Y/L)ontheverticalaxisandcapitalperworker(K/L)onthehorizontalaxistheequilibriumconditionforbalancedgrowthcanalsobeshownK/L=s/(n+g+)

38Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.BuildingandSolvinganEconom38Figure3.6-EquilibriumOutputperWorker39Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure3.6-EquilibriumOutpu39TheAdvantagesofUsingAlgebrabestwaytosummarizecause-and-effectbehavioralrelationshipsallowsustoconsiderdifferentpossiblesystematicrelationshipsbychangingthevalueofparameters40Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.TheAdvantagesofUsingAlgebr40Figure3.7-ASingleEquation,aHost

ofRelationships41Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure3.7-ASingleEquation41Figure3.8-ChangingParameterValuesandtheShapeoftheCobb-DouglasProductionFunction42Copyright©2002byTheMcGraw-HillCompanies,Inc.Allrightsreserved.Figure3.8-ChangingParamete42Figure3.9-TheEffectofChangesintheEfficiencyofLaborontheShape