10 理性消费者ppt课件.ppt

,chapter:,10,Krugman/WellsEconomics,2009WorthPublishers,TheRationalConsumer,HowconsumerschoosetospendtheirincomeongoodsandservicesWhyconsumersmakechoicesbymaximizingutility,ameasureofsatisfactionfromconsumptionWhytheprincipleofdiminishingmarginalutilityappliestotheconsumptionofmostgoodsandservicesHowtousemarginalanalysistofindtheoptimalconsumptionbundleWhatincomeandsubstitutioneffectsare,OpportunityCostandDecisions,Theutilityofaconsumerisameasureofthesatisfactiontheconsumerderivesfromconsumptionofgoodsandservices.Anindividualsconsumptionbundleisthecollectionofallthegoodsandservicesconsumedbythatindividual.Anindividualsutilityfunctiongivesthetotalutilitygeneratedbyhisorherconsumptionbundle.Theunitofutilityisautil.,Utilityfunction,MarginalUtilityCurve,7,9,8,6,5,4,3,2,1,0,70,60,50,40,30,20,10,Totalutility(utils),Quantityofclams,7,9,8,6,5,4,3,2,1,16,14,12,10,8,6,4,2,0,2,Marginalutilityperclams(utils),Quantityofclams,(a),CassiesUtilityFunction,(,b,),CassiesMarginalUtilityCurve,CassiesTotalUtilityandMarginalUtility,CassiesTotalUtilityandMarginalUtility,Cassiestotalutilitydependsonherconsumptionoffriedclams.Itincreasesuntilitreachesitsmaximumutilitylevelof64utilsat8clamsconsumedanddecreasesafterthat.Themarginalutilitycurveslopesdownwardduetodiminishingmarginalutility;eachadditionalclamgivesCassielessutilitythanthepreviousclam.,ThePrincipleofDiminishingMarginalUtility,Themarginalutilityofagoodorserviceisthechangeintotalutilitygeneratedbyconsumingoneadditionalunitofthatgoodorservice.Themarginalutilitycurveshowshowmarginalutilitydependsonthequantityofagoodorserviceconsumed.Theprincipleofdiminishingmarginalutilitysaysthateachsuccessiveunitofagoodorserviceconsumedaddslesstototalutilitythanthepreviousunit.,BudgetsandOptimalConsumption,Abudgetconstraintrequiresthatthecostofaconsumersconsumptionbundlebenomorethantheconsumerstotalincome.Aconsumersconsumptionpossibilitiesisthesetofallconsumptionbundlesthatcanbeconsumedgiventheconsumersincomeandprevailingprices.Aconsumersbudgetlineshowstheconsumptionbundlesavailabletoaconsumerwhospendsallofhisorherincome.,1,0,2,3,4,5,10,8,6,4,2,A,B,C,D,E,F,AffordableconsumptionbundlesthatcostallofSammysincome,SammysBudgetLine,BL,Affordableconsumptionbundles,Unaffordableconsumptionbundles,Quantityofclams(pounds),Quantityofpotatoes(pounds),TheBudgetLine,SammysUtilityfromConsumption,OptimalConsumptionChoice,Theoptimalconsumptionbundleistheconsumptionbundlethatmaximizesaconsumerstotalutilitygivenhisorherbudgetconstraint.,SammysBudgetandTotalUtility,Sammystotalutilityisthesumoftheutilityhegetsfromclamsandtheutilityhegetsfrompotatoes.,Quantityofpotatoes(pounds),5,4,3,2,1,0,10,8,6,4,2,A,A,B,B,C,C,D,D,E,E,BL,Utilityfunction,F,F,5,4,3,2,1,0,80,70,60,50,40,30,20,10,Quantityofclams(pounds),0,2,4,6,8,10,(a),SammysBudgetLine,(b),SammysUtilityFunction,Theoptimalconsumptionbundle,Quantityofclams(pounds),Quantityofpotatoes(pounds),maximizestotalutilitygiventhebudgetconstraint,Totalutility(utils),OptimalConsumptionBundle,SammystotalutilityismaximizedatbundleC,whereheconsumes2poundsofclamsand6poundsofpotatoes.ThisisSammysoptimalconsumptionbundle.,SpendingtheMarginalDollar,Themarginalutilityperdollarspentonagoodorserviceistheadditionalutilityfromspendingonemoredollaronthatgoodorservice.,SammysMarginalUtilityperDollar,MarginalUtilityperDollar,IfSammyhas,infact,chosenhisoptimalconsumptionbundle,hismarginalutilityperdollarspentonclamsandpotatoesmustbeequal.,6,5,4,3,2,1,MU,P,/,P,P,C,5,4,3,2,1,0,0,2,4,6,8,10,Totalutility(utils),Quantityofclams(pounds),Quantityofpotatoes(pounds),Attheoptimalconsumptionbundle,themarginalutilityperdollarspentonclamsisequaltothemarginalutilityperdollarspentonpotatoes.,OptimalConsumptionRule,Theoptimalconsumptionrulesaysthatwhenaconsumermaximizesutility,themarginalutilityperdollarspentmustbethesameforallgoodsandservicesintheconsumptionbundle.,FromUtilitytotheDemandCurve,Themainreasonforstudyingconsumerbehavioristounderstandhowthedownwardslopeofthemarketdemandcurveisexplainedbytheutility-maximizingbehaviorofindividualconsumers.,MarginalUtility,theSubstitutionEffect,andtheLawofDemand,Thesubstitutioneffectofachangeinthepriceofagoodisthechangeinthequantityconsumedofthatgoodastheconsumersubstitutesthegoodthathasbecomerelativelycheaperforthegoodthathasbecomerelativelymoreexpensive.,TheIncomeEffect,Theincomeeffectofachangeinthepriceofagoodisthechangeinthequantityconsumedofthatgoodthatresultsfromachangeintheconsumerspurchasingpowerduetothechangeinthepriceofthegood.NormalGoodsInferiorGoodsGiffenGoods,Consumersmaximizeameasureofsatisfactioncalledutility.Eachconsumerhasautilityfunctionthatdeterminestheleveloftotalutilitygeneratedbyhisorherconsumptionbundle,thegoodsandservicesthatareconsumed.Agoodsorservicesmarginalutilityistheadditionalutilitygeneratedbyconsumingonemoreunitofthegoodorservice.Weusuallyassumethattheprincipleofdiminishingmarginalutilityholds:consumptionofanotherunitofagoodorserviceyieldslessadditionalutilitythanthepreviousunit.,Abudgetconstraintlimitsaconsumersspendingtonomorethanhisorherincome.Itdefinestheconsumersconsumptionpossibilities,thesetofallaffordableconsumptionbundles.Aconsumerwhospendsallofhisorherincomewillchooseaconsumptionbundleonthebudgetline.Anindividualchoosestheconsumptionbundlethatmaximizestotalutility,theoptimalconsumptionbundle.Theoptimalconsumptionrulesaysthatattheoptimalconsumptionbundlethemargin