管理经济学托马斯版Chap005

Chapter5:TheoryofConsumerBehaviorMcGraw-Hill/IrwinCopyright©2011bytheMcGraw-HillCompanies,Inc.Allrightsreserved.TheConsumer’sOptimizationProblemIndividualconsumptiondecisionsaremadewiththegoalofmaximizingtotalsatisfactionfromconsumingvariousgoodsandservicesSubjecttotheconstraintthatspendingongoodsexactlyequalstheindividual’smoneyincomeConsumerTheoryAssumesbuyersarecompletelyinformedabout:RangeofproductsavailablePricesofallproductsCapacityofproductstosatisfyTheirincomeRequiresthatconsumerscanrankallconsumptionbundlesbasedonthelevelofsatisfactiontheywouldreceivefromconsumingthevariousbundlesTypicalConsumptionBundlesforTwoGoods,X&Y

(Figure5.1)PropertiesofConsumerPreferencesCompletenessForeverypairofconsumptionbundles,AandB,theconsumercansayoneofthefollowing:AispreferredtoBBispreferredtoATheconsumerisindifferentbetweenAandBTransitivityIfAispreferredtoB,andBispreferredtoC,thenA

mustbepreferredtoCNonsatiationMoreofagoodisalwayspreferredtolessUtilityBenefitsconsumersobtainfromgoods&servicestheyconsumeisutilityAutilityfunctionshowsanindividual’sperceptionoftheutilitylevelattainedfromconsumingeachconceivablebundleofgoodsIndifferenceCurvesLocusofpointsrepresentingdifferentbundlesofgoods,eachofwhichyieldsthesameleveloftotalutilityNegativelysloped&convexTypicalIndifferenceCurve(Figure5.2)MarginalRateofSubstitutionMRSshowstherateatwhichonegoodcanbesubstitutedforanotherwhilekeepingutilityconstantNegativeoftheslopeoftheindifferencecurveDiminishesalongtheindifferencecurveasXincreases&YdecreasesRatioofthemarginalutilitiesofthegoodsSlopeofanIndifferenceCurve&theMRS

(Figure5.3)QuantityofgoodXQuantityofgoodY0IC(360,320)600800ABTT’360320IndifferenceMap(Figure5.4)QuantityofYQuantityofXIIIIIIIVMarginalUtilityAdditiontototalutilityattributabletotheadditionofoneunitofagoodtothecurrentrateofconsumption,holdingconstanttheamountsofallothergoodsconsumedConsumer’sBudgetLineShowsallpossiblecommoditybundlesthatcanbepurchasedatgivenpriceswithafixedmoneyincomeorConsumer’sBudgetConstraint

(Figure5.5)TypicalBudgetLine(Figure5.6)QuantityofYQuantityofX••ABShiftingBudgetLines(Figure5.7)PanelB–ChangesinpriceofX200100AB250DRN120240QuantityofYQuantityofXPanelA–ChangesinmoneyincomeQuantityofYQuantityofXAB100FZ80160200125CUtilityMaximizationUtilitymaximizationsubjecttoalimitedmoneyincomeoccursatthecombinationofgoodsforwhichtheindifferencecurveisjusttangenttothebudgetlineUtilityMaximizationConsumerallocatesincomesothatthemarginalutilityperdollarspentoneachgoodisthesameforallcommoditiespurchasedConstrainedUtilityMaximization(Figure5.8)A•IC••BIIRTQuantityofburgersQuantityofpizzas08020100406010203040507010903050•EIII•DIV4515IndividualConsumerDemandAnindividual’sdemandcurveforaspecificcommodityrelatesutility-maximizingquantitiespurchasedtomarketpricesMoneyincome&pricesheldconstantSlopeofdemandcurveillustrateslawofdemand—quantitydemandedvariesinverselywithpriceDerivingaDemandCurve(Figure5.9)QuantityofYPriceofX($)QuantityofXQuantityofX10020012510000Px=$10Px=$5Px=$89065509065505810DemandforXMarketDemand&MarginalBenefitListofprices&quantitiesconsumersarewilling&abletopurchaseateachprice,allelseconstantDerivedbyhorizontallysummingdemandcurvesforallindividualsinmarketBecausepricesalongmarketdemandmeasuretheeconomicvalueofeachunitofthegood,itcanbeinterpretedasthemarginalbenefitcurveforagoodDerivationofMarketDemand(Table5.1)

QuantitydemandedPriceConsumer1Consumer2Consumer3Marketdemand$62154331213581007101350680143253161219DerivationofMarketDemandFigure(5.10)Substitution&IncomeEffectsWhenpricechanges,totalchangeinquantitydemandediscomposedoftwopartsSubstitutioneffectIncomeeffectSubstitution&IncomeEffectsSubstitutioneffectChangeinconsumptionofagoodafterachangeinitsprice,whentheconsumerisforcedbyachangeinmoneyincometoconsumeatsomepointontheoriginalindifferencecurveIncomeeffectChangeinconsumptionofagoodresultingstrictlyfromachangeinpurchasingpowerIncome&SubstitutionEffects:ADecreaseinPx

(Figure5.12)Totaleffectofpricedecrease=Substitutioneffect+Incomeeffect9=5+4Totaleffectofpricedecrease=Substitutioneffect+Incomeeffect3=5+(-2)Substitution&IncomeEffectsConsiderthesubstitutioneffectalone:AmountofgoodconsumedmustvaryinverselywithpriceIncomeeffectreinforcesthesubstitutioneffectforanormalgood&offsetsitforaninf