管理经济学托马斯版Chap005

Chapter5:TheoryofConsumerBehaviorMcGraw-Hill/IrwinCopyright©2011bytheMcGraw-HillCompanies,Inc.Allrightsreserved.5-2TheConsumer’sOptimizationProblem•Individualconsumptiondecisionsaremadewiththegoalofmaximizingtotalsatisfactionfromconsumingvariousgoodsandservices•Subjecttotheconstraintthatspendingongoodsexactlyequalstheindividual’smoneyincome5-3ConsumerTheory•Assumesbuyersarecompletelyinformedabout:•Rangeofproductsavailable•Pricesofallproducts•Capacityofproductstosatisfy•Theirincome•Requiresthatconsumerscanrankallconsumptionbundlesbasedonthelevelofsatisfactiontheywouldreceivefromconsumingthevariousbundles5-4TypicalConsumptionBundlesforTwoGoods,X&Y(Figure5.1)5-5PropertiesofConsumerPreferences•Completeness•Foreverypairofconsumptionbundles,AandB,theconsumercansayoneofthefollowing:AispreferredtoBBispreferredtoATheconsumerisindifferentbetweenAandB•Transitivity•IfAispreferredtoB,andBispreferredtoC,thenAmustbepreferredtoC•Nonsatiation•Moreofagoodisalwayspreferredtoless5-6Utility•Benefitsconsumersobtainfromgoods&servicestheyconsumeisutility•Autilityfunctionshowsanindividual’sperceptionoftheutilitylevelattainedfromconsumingeachconceivablebundleofgoods5-7IndifferenceCurves•Locusofpointsrepresentingdifferentbundlesofgoods,eachofwhichyieldsthesameleveloftotalutility•Negativelysloped&convex5-8TypicalIndifferenceCurve(Figure5.2)5-9MarginalRateofSubstitution•MRSshowstherateatwhichonegoodcanbesubstitutedforanotherwhilekeepingutilityconstant•Negativeoftheslopeoftheindifferencecurve•DiminishesalongtheindifferencecurveasXincreases&Ydecreases•RatioofthemarginalutilitiesofthegoodsXYMUYMRSXMU5-10SlopeofanIndifferenceCurve&theMRS(Figure5.3)QuantityofgoodXQuantityofgoodY0IC(360,320)600800ABTT’3603205-11IndifferenceMap(Figure5.4)QuantityofYQuantityofXIIIIIIIV5-12MarginalUtility•Additiontototalutilityattributabletotheadditionofoneunitofagoodtothecurrentrateofconsumption,holdingconstanttheamountsofallothergoodsconsumedMUUX5-13Consumer’sBudgetLine•ShowsallpossiblecommoditybundlesthatcanbepurchasedatgivenpriceswithafixedmoneyincomeXYMPXPYXYYPMYXPPor5-14Consumer’sBudgetConstraint(Figure5.5)5-15TypicalBudgetLine(Figure5.6)QuantityofYQuantityofXXYYPMYXPP••ABYMPXMP5-16ShiftingBudgetLines(Figure5.7)PanelB–ChangesinpriceofX200100AB250DRN120240QuantityofYQuantityofXPanelA–ChangesinmoneyincomeQuantityofYQuantityofXAB100FZ80160200125C5-17UtilityMaximization•UtilitymaximizationsubjecttoalimitedmoneyincomeoccursatthecombinationofgoodsforwhichtheindifferencecurveisjusttangenttothebudgetlineXXYYMUPYMRSXMUP5-18UtilityMaximization•ConsumerallocatesincomesothatthemarginalutilityperdollarspentoneachgoodisthesameforallcommoditiespurchasedXYXYMUMUPP5-19ConstrainedUtilityMaximization(Figure5.8)A•IC••BIIRTQuantityofburgersQuantityofpizzas08020100406010203040507010903050•EIII•DIV45155-20IndividualConsumerDemand•Anindividual’sdemandcurveforaspecificcommodityrelatesutility-maximizingquantitiespurchasedtomarketprices•Moneyincome&pricesheldconstant•Slopeofdemandcurveillustrateslawofdemand—quantitydemandedvariesinverselywithprice5-21DerivingaDemandCurve(Figure5.9)QuantityofYPriceofX($)QuantityofXQuantityofX10020012510000Px=$10Px=$5Px=$89065509065505810DemandforX5-22MarketDemand&MarginalBenefit•Listofprices&quantitiesconsumersarewilling&abletopurchaseateachprice,allelseconstant•Derivedbyhorizontallysummingdemandcurvesforallindividualsinmarket•Becausepricesalongmarketdemandmeasuretheeconomicvalueofeachunitofthegood,itcanbeinterpretedasthemarginalbenefitcurveforagood5-23DerivationofMarketDemand(Table5.1)QuantitydemandedPriceConsumer1Consumer2Consumer3Marketdemand$621543312135810071013506801432531612195-24DerivationofMarketDemandFigure(5.10)5-25Substitution&IncomeEffects•Whenpricechanges,totalchangeinquantitydemandediscomposedoftwoparts•Substitutioneffect•Incomeeffect5-26Substitution&IncomeEffects•Substitutioneffect•Changeinconsumptionofagoodafterachangeinitsprice,whentheconsumerisforcedbyachangeinmoneyincometoconsumeatsomepointontheoriginalindifferencecurve•Incomeeffect•Changeinconsumptionofagoodresultingstrictlyfromachangeinpurchasingpower5-27Income&SubstitutionEffects:ADecreaseinPx(Figure5.12)Totaleffectofpricedecrease=Substitutioneffect+Incomeeffect9=5+4Totaleffectofpricedecrease=Substitutioneffect+Incomeeffect3=5+(-2)5-28Substitution&IncomeEffects•Considerthesubstitutioneffectalone:•Amountofgoodconsumedmustvaryinverselywithprice•Incomeeffectreinforcesthesubstitutioneffectforanormalgood&offsetsitforaninferiorgood5-29SummaryofSubstitution&IncomeEffects(Table5.2)SubstitutionEffectIncomeEffectPriceofXdecreases:NormalGoodInferiorGoodPriceofXincreases:NormalGoodInferiorGoodXrisesXrisesXrisesXrisesXfallsXfallsXfallsXfalls