ch01-introduction.ppt

ch01-introduction.ppt

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1INTRODUCTIONECONOMICMODELS2TheoreticalModelsEconomistsusemodelstodescribeeconomicactivitiesWhilemosteconomicmodelsareabstractionsfromreality,theyprovideaidinunderstandingeconomicbehavior3VerificationofEconomicModelsTherearetwogeneralmethodsusedtoverifyeconomicmodels:

directapproachestablishesthevalidityofthemodelsassumptionsindirectapproachshowsthatthemodelcorrectlypredictsreal-worldevents4VerificationofEconomicModelsWecanusetheprofit-maximizationmodeltoexaminetheseapproachesisthebasicassumptionvalid?

dofirmsreallyseektomaximizeprofits?

canthemodelpredictthebehaviorofreal-worldfirms?

5FeaturesofEconomicModelsCeterisParibusassumptionOptimizationassumptionDistinctionbetweenpositiveandnormativeanalysis6CeterisParibusAssumptionCeterisParibusmeans“otherthingsthesame”（如果其他条件不变）Economicmodelsattempttoexplainsimplerelationshipsfocusontheeffectsofonlyafewforcesatatimeothervariablesareassumedtobeunchangedduringtheperiodofstudy7OptimizationAssumptionsManyeconomicmodelsbeginwiththeassumptionthateconomicactorsarerationallypursuingsomegoalconsumersseektomaximizetheirutilityfirmsseektomaximizeprofits（orminimizecosts）governmentregulatorsseektomaximizepublicwelfare8OptimizationAssumptionsOptimizationassumptionsgenerateprecise,solvablemodelsOptimizationmodelsappeartobeperformfairlywellinexplainingreality9Positive-NormativeDistinctionPositiveeconomictheoriesseektoexplaintheeconomicphenomenathatisobservedNormativeeconomictheoriesfocusonwhat“should”bedone10TheEconomicTheoryofValueEarlyEconomicThought“value”wasconsideredtobesynonymouswith“importance”sincepricesweredeterminedbyhumans,itwaspossibleforthepriceofanitemtodifferfromitsvaluepricesvaluewerejudgedtobe“unjust”11TheEconomicTheoryofValueTheFoundingofModernEconomicsthepublicationofAdamSmithsTheWealthofNationsisconsideredthebeginningofmoderneconomicsdistinguishingbetween“value”and“price”continued（illustratedbythediamond-waterparadox）thevalueofanitemmeantits“valueinuse”thepriceofanitemmeantits“valueinexchange”12TheEconomicTheoryofValueLaborTheoryofExchangeValuetheexchangevaluesofgoodsaredeterminedbywhatitcoststoproducethemthesecostsofproductionwereprimarilyaffectedbylaborcoststherefore,theexchangevaluesofgoodsweredeterminedbythequantitiesoflaborusedtoproducethemproducingdiamondsrequiresmorelaborthanproducingwater13TheEconomicTheoryofValueTheMarginalistRevolutiontheexchangevalueofanitemisnotdeterminedbythetotalusefulnessoftheitem,butrathertheusefulnessofthelastunitconsumedbecausewaterisplentiful,consuminganadditionalunithasarelativelylowvaluetoindividuals14TheEconomicTheoryofValueMarshallianSupply-DemandSynthesisAlfredMarshallshowedthatsupplyanddemandsimultaneouslyoperatetodeterminepricepricesreflectboththemarginalevaluationthatconsumersplaceongoodsandthemarginalcostsofproducingthegoodswaterhasalowmarginalvalueandalowmarginalcostofproductionLowpricediamondshaveahighmarginalvalueandahighmarginalcostofproductionHighprice15Supply-DemandEquilibriumQuantityperperiodPriceP*Q*DThedemandcurvehasanegativeslopebecausethemarginalvaluefallsasquantityincreasesSThesupplycurvehasapositiveslopebecausemarginalcostrisesasquantityincreasesEquilibriumQD=Qs16GeneralEquilibriumModelstheMarshallianmodelisapartialequilibriummodelfocusesonlyononemarketatatimetoanswermoregeneralquestions,weneedamodeloftheentireeconomyneedtoincludetheinterrelationshipsbetweenmarketsandeconomicagentsTheEconomicTheoryofValue17TheproductionpossibilitiesfrontiercanbeusedasabasicbuildingblockforgeneralequilibriummodelsAproductionpossibilitiesfrontiershowsthecombinationsoftwooutputsthatcanbeproducedwithaneconomysresourcesTheEconomicTheoryofValue18TheproductionpossibilityfrontierremindsusthatresourcesarescarceScarcitymeansthatwemustmakechoiceseachchoicehasopportunitycoststheopportunitycostsdependonhowmuchofeachgoodisproducedAProductionPossibilityFrontier19WelfareEconomicstoolsusedingeneralequilibriumanalysishavebeenusedfornormativeanalysisconcerningthedesirabilityofvariouseconomicoutcomeseconomistsFrancisEdgeworthandVilfredoParetohelpedtoprovideaprecisedefinitionofeconomicefficiencyanddemonstratedtheconditionsunderwhichmarketscanattainthatgoalTheEconomicTheoryofValue20ModernToolsClarificationofthebasicbehavioralassumptionsaboutindividualandfirmbehaviorCreationofnewtoolstostudymarketsIncorporationofuncertaintyandimperfectinformationintoeconomicmodelsIncreasinguseofcomputerstoanalyzedata21ImportantPoint