管理经济学（第14版） 课件 第5章　消费者行为理论

Chapter05TheoryofConsumerBehaviorMANAGERIALECONOMICSFoundationsofBusinessAnalysisandStrategyFourteenthEditionCHRISTOPHERR.THOMAS©McGrawHillLLC.Allrightsreserved.NoreproductionordistributionwithoutthepriorwrittenconsentofMcGrawHillLLC.LearningOutcomes5.1 Explaintheconceptofutilityandbasicassumptionsunderlyingconsumerpreferences.5.2 Definetheconceptofindifferencecurvesandexplainthepropertiesofindifferencecurvesandmaps.5.3 Constructaconsumer’sbudgetlineandexplainhowtorotateorshiftthelinewhenpricesorincomechange.5.4 Derive/interpretequilibriumconditionsforaconsumertobemaximizingutilitysubjecttoabudgetconstraint.5.5 Useindifferencecurvestoderiveademandcurveforanindividualconsumerandconstructamarketdemandcurvebyhorizontallysummingindividualdemands.5.6 Defineacornersolutionandexplaintheconditionthatcreatesacornersolution.5.7 Identifyandmeasurethesubstitutionandincomeeffectsofapricechange.2TheConsumer’sOptimizationProblemIndividualconsumptiondecisionsaremadewiththegoalofmaximizingtotalsatisfactionfromconsumingvariousgoodsandservices.Subjecttotheconstraintthatspendingongoodsexactlyequalstheindividual’smoneyincome.Combinationsofgoodsorservicesarecalledconsumptionbundles.3Figure5.1TypicalConsumptionBundlesforTwoGoods,XandYAccessthetextalternativeforslideimages.4ConsumerTheoryAssumesbuyersarecompletelyinformedabout:Rangeofproductsavailable.Pricesofallproducts.Capacityofproductstosatisfytheirincomes.Requiresthatconsumerscanrankallconsumptionbundlesbasedonthelevelofsatisfactiontheywouldreceivefromconsumingthevariousbundles.5PropertiesofConsumerPreferencesCompletenessConsumersareabletorankallconceivablebundlesofcommodities.Forconsumptionbundles,AandB,theconsumercansayoneofthefollowing:AispreferredtoB.BispreferredtoA.TheconsumerisindifferentbetweenAandB.TransitivityIfAispreferredtoB,andBispreferredtoC,thenA

mustbepreferredtoC.NonsatiationMoreofagoodisalwayspreferredtoless.6UtilityBenefitsconsumersobtainfromgoodsandservicestheyconsumeisutility.Autilityfunction

isanequationthatshowsanindividual’sperceptionoftheutilitylevelattainedfromconsumingeachconceivablebundleofgoods:U=f(X,Y)7IndifferenceCurvesAnindifferencecurveisasetofpointsrepresentingdifferentbundlesofgoodsandservices,eachofwhichyieldsthesameleveloftotalutility.Indifferencecurvesaredownward-slopingandconvex.8Figure5.2ATypicalIndifferenceCurveAccessthetextalternativeforslideimages.9MarginalRateofSubstitutionThemarginalrateofsubstitution(M

R

S)measuresthenumberofunitsofYthatmustbegivenupperunitofXaddedsoastomaintainaconstantlevelofutility.Negativeoftheslopeoftheindifferencecurve.DiminishesalongtheindifferencecurveasXincreasesandYdecreases.10Figure5.3TheSlopeofanIndifferenceCurveandtheMRSAccessthetextalternativeforslideimages.11IndifferenceMapsAnindifferencemapconsistsofseveralindifferencecurves.Thehigher(orfurthertotheright)anindifferencecurve,thegreaterthelevelofutilityassociatedwiththecurve.Combinationsofgoodsonhigherindifferencecurvesarepreferredtocombinationsonlowercurves.12Figure5.4IndifferenceMapAccessthetextalternativeforslideimages.13MarginalUtilityAdditiontototalutilityattributabletotheadditionofoneunitofagoodtothecurrentrateofconsumption,holdingconstanttheamountsofallothergoodsconsumed.14Consumer’sBudgetLineShowsallpossiblebundlesofgoodsthatcanbepurchasedatgivenpricesiftheentireincomeisspent.15Figure5.5AConsumer’sBudgetConstraintAccessthetextalternativeforslideimages.16Figure5.6ATypicalBudgetLineAccessthetextalternativeforslideimages.17Figure5.7ShiftingBudgetLinesAccessthetextalternativeforslideimages.18UtilityMaximizationUtilitymaximizationsubjecttoalimitedincomeoccursatthecombinationofgoodsforwhichtheindifferencecurveisjusttangenttothebudgetline.Consumerallocatesincomesothatthemarginalutilityperdollarspentoneachgoodisthesameforallcommoditiespurchased.19Figure5.8ConstrainedUtilityMaximizationAccessthetextalternativeforslideimages.20UtilityMaximization,NGoodsTheutilitymaximizationprincipleiseasilyextendedtocoveranynumberofgoods:21IndividualConsumerDemandAnindividual’sdemandcurveforaspecificcommodityrelatesutility-maximizingquantitiespurchasedtomarketprices.Incomeandpricesofallothergoodsheldconstant.Slopeofdemandcurveillustratesthelawofdemand:quantitydemandedvariesinverselywithprice.22Figure5.9DerivingaDemandCurveAccessthetextalternativeforslideimages.23MarketDemandandMarginalBenefitMarketdemandisalistofpricesandquantitiesconsumersarewillingandabletopurchaseateachprice,allelseconstant.Derivedbyhorizontallysummingdemandcurvesforallindividualsinmarket.Becausepricesalongmarketdemandmeasuretheeconomicvalueofeachunitofthegood,marketdemandcanbeinterpretedasthemarginalbenefitcurveforagood.24Table5.1AggregatingIndividualDemandsQuantityDemandedPriceConsumer1Consumer2Consumer3MarketDemand$6300355106483112310541921276251131083125Figure5.10DerivationofMarketDemandAccessthetextalternativeforslideimages.26CornerSolution1Inmanycasesconsumersspendtheirentirebudgetandchoosetopurchasenoneofsomespecificgood.Acornersolutionexistswhentheutilitymaximizingbundleliesatoneoftheendpointsofthebudgetlineandtheconsumerchoosestoconsumezerounitsofagood.27CornerSolution2ForgoodsXandY,acornersolution,inwhichtheconsumerpurchasesnoneofgoodX,resultswhen:Ingeneral,acornersolution,inwhichtheconsumerpurchasesnoneofgoodX,resultswhen:28Figure5.11CornerSolution:X*=0Accessthetextalternativeforslideimages.29SubstitutionandIncomeEffectsThesubstitutioneffect

isthechangeintheconsumptionofagoodthatwouldresultiftheconsumerremainedonthesameindifferencecurveafterthepriceofagoodchanges.Theincomeeffectisthechangeintheconsumptionofagoodresultingstrictlyfromachangeinpurchasingpowerafterthepriceofagoodchanges.Thetotaleffectisthesumofthesubstitutionandincomeeffects.AGiffengoodisagoodforwhichthedemandcurveisupward-slopingandtheoreticallyoccurswhentheincomeeffectofaninferiorgoodoutweighsthesubstitutioneffect.30Figure5.12TheSubstitutionEffectWhenPriceDecreasesAccessthetextalternativeforslideimages.31Figure5.13SubstitutionandIncomeEffects:ADecreaseinPxAccessthetextalternativeforslideimages.32Figure5.14SubstitutionandIncomeEffects:AnIncreaseinPxAccessthetextalternativeforslideimages.33Table5.2SummaryofSubstitutionandIncomeEffectsforaChangeinthePriceofXSubstitutionEffectIncomeEffectPriceofXdecreases:NormalgoodXrisesXrisesInferiorgoodXrisesXfallsPriceofXincreases:NormalgoodXfallsXfallsInferiorgoodXfallsXrises34Summary1Basicpremiseforanalyzingconsumerbehavioristhatindividualsmakeconsumptiondecisionswiththegoalofmaximizingtheirtotalsatisfactionfromconsumingvariousgoodsandservices,subjecttotheconstraintthattheirspendingongoodsexactlyequalstheirincomes.Thebenefitconsumersobtainfromthegoodsandservicestheyconsumeiscalledutility.Theutilityfunctionshowsanindividual'sperceptionofthelevelofutilityfromconsumingeachconceivablebundleofgoods.Marginalutilityistheadditiontototalutilityattributabletoaddingoneunitofagood,holdingconstanttheamountsofallothergoodsconsumed.Themarginalrateofsubstitution(MRS)showstherateatwhichonegoodcanbesubstitutedforanotherwhilekeepingutilityconstant.35Summary2Anindifferencecurveisasetofpointsrepresentingdifferentbundlesofgoodsandservices,eachofwhichyieldsthesameleveloftotalutility.Theconsumer’sbudgetlineshowsthesetofallconsumptionbundlesthatcanbepurchasedatgivenpricesandincomeiftheentireincomeisspent.Aconsumermaximizesutilitysubjecttoalimitedincomeatthecombinationofgoodsforwhichtheindifferencecurveisjusttangenttothebudgetline.Atthiscombination,theMRSisequaltothepriceratio.36Summary3Anindividualconsumer’sdemandcurverelatesutility-maximizingquantitiestomarketprices,holdingconstantincomeandpricesofallothergoods.Marketdemandisderivedbyhorizontallysummingthedemandcurvesforallindividualsinthemarket.Whenaconsumerspendstheentirebudgetandchoosestopurchasenoneofaspecificgood,thisoutcomeiscalledacornersolution.Pricechangeshavetwoeffects:asubstitutionandanincomeeffect.37EndofMainContent©McGrawHillLLC.Allrightsreserved.NoreproductionordistributionwithoutthepriorwrittenconsentofMcGrawHillLLC.AccessibilityContent:TextAlternativesforImages39Figure5.1TypicalConsumptionBundlesforTwoGoods,XandY-TextAlternativeReturntoparent-slidecontainingimages.TheverticalaxisislabeledasthequantityofgoodYrangingfrom0to70inincrementsof10.ThehorizontalaxisislabeledasthequantityofgoodXrangingfrom0to70inincrementsof10.PointAisplottedat(10,60),pointBisplottedat(20,40),pointCisplottedat(40,20),pointDisplottedat(50,15),pointEisplottedat(20,50),andpointFisplottedat(40,10).Asolidlinefromtheverticalaxisandadashedlinefromthehorizontalaxisconnectseachplot.Notethatthecoordinatevaluesareactualvalues.Returntoparent-slidecontainingimages.40Figure5.2ATypicalIndifferenceCurve

-TextAlternativeReturntoparent-slidecontainingimages.TheverticalaxisislabeledasthequantityofgoodYrangingfrom0to70inincrementsof10.ThehorizontalaxisislabeledasthequantityofgoodXrangingfrom0to70inincrementsof10.Aconcave-updecreasingcurve,labeledI,passesthroughfourpointsA,B,C,andD.Thelabeledpointsonthecurveareasfollows:A(10,60),B(20,40),C(40,20)andD(50,15).Atangent,labeledR,isdrawnonthecurveatpointA(10,60).Anothertangent,labeledT,isdrawnonthecurveatpointC(40,20).Notethatthecoordinatevaluesareactualvalues.Returntoparent-slidecontainingimages.41Figure5.3TheSlopeofanIndifferenceCurveandtheMRS

-TextAlternativeReturntoparent-slidecontainingimages.TheverticalaxisislabeledasthequantitiesofgoodsYwithscales0,320,and600.ThehorizontalaxisislabeledasthequantityofgoodXwithscales0,360,and800.Aconcave-updecreasingcurve,labeledI,passesthroughthepointatC(360,320).Atangent,labeledT,Tprime,isdrawnonthecurveatpointC.ThetangentisextendedtopointA(0,600)andpointB(800,0)throughdashedlines.Thegraphenclosesthepointofcontactofthetangentandthecurve.Ablow-upsectionofpointCwithtangentlineT,Tprimeshowsright-angledpoints(360,320),andadashedlinejoiningpoints(361,319.25).Thedistancebetween320and319.25is0.75.Thedistancebetween360and361is1.Notethattheabove-mentionedcoordinatevaluesareactualvalues.Returntoparent-slidecontainingimages.42Figure5.4IndifferenceMap

-TextAlternativeReturntoparent-slidecontainingimages.TheverticalaxisislabeledasquantityofYandthehorizontalaxisislabeledasquantityofX.Fourconcave-updecreasingcurveslabeled1,2,3,and4aredrawnfromthetoplefttothebottomrightofthegraph.Returntoparent-slidecontainingimages.43Figure5.5AConsumer’sBudgetConstraint

-TextAlternativeReturntoparent-slidecontainingimages.TheverticalaxisislabeledasthequantityofYrangingfrom0to150inincrementsof50.ThehorizontalaxisislabeledasthequantityofXrangingfrom0to200inincrementsof50.AlinewithanegativeslopestartsatA(0,100),passesthroughpointsC(40,80)andD(120,40),andendsatB(200,0).Theslopeofthelineislabelednegative1over2.TheverticalandhorizontallinesfromthehorizontalaxisandverticalaxisconnectplotsCandD.ThegraphenclosestheblowupslopeatpointD.Theriseislabeled1over2andtherunislabeled1forming90degrees.TherunintersectsthelineatpointE(121,39.5).TheslopebetweenCandDformsanangleof90degrees.Theheightoftheangleismarked10andthebaseis20.Notethattheabove-mentionedcoordinatevaluesareactualvalues.Returntoparent-slidecontainingimages.44Figure5.6ATypicalBudgetLine

-TextAlternativeReturntoparent-slidecontainingimages.TheverticalaxisislabeledasthequantityofYandthehorizontalaxisislabeledasthequantityofX.Theline,labeledYequalsMoverPsubscriptYminusPsubscriptXoverPsubscriptYtimesX,withanegativeslopestartsatpointAonthey-axisandendsatpointBonthex-axis.PointAislabeledMoverPsubscriptYandpointBislabeledMoverPsubscriptX.Returntoparent-slidecontainingimages.45Figure5.7ShiftingBudgetLines

-TextAlternativeReturntoparent-slidecontainingimages.ThegraphistitledPanelA-changesinincome.TheverticalaxisislabeledasthequantityofYwithscales0,80,100,and120.ThehorizontalaxisislabeledasthequantityofXwithscales0,160,200,and240.Threedecreasingdiagonallinesaredrawn.ThefirstlinestartsatF(0,80)andendsatZ(160,0).ThesecondlinestartsatA(0,100)andendsatB(200,0).ThethirdlinestartsatR(0,120)andendsatN(240,0).Notethatthecoordinatevaluesareactualvalues.ThegraphistitledPanelB-changesinthepriceofX.TheverticalaxisislabeledasthequantityofYrangingfrom0to100.ThehorizontalaxisislabeledasthequantityofXwithscales0,125,200,and250.Threedecreasingdiagonallinesaredrawn.ThefirstlinestartsatA(0,100)andendsatC(125,0).ThesecondlinestartsatA(0,100)andendsatB(200,0).ThethirdlinestartsatA(0,100)andendsatD(250,0).Notethatthecoordinatevaluesareactualvalues.Returntoparent-slidecontainingimages.46Figure5.8ConstrainedUtilityMaximization

-TextAlternativeReturntoparent-slidecontainingimages.Theverticalaxisislabeledasthequantitiesofpizzasrangingfrom0to50inincrementsof10.Thehorizontalaxisislabeledasthequantitiesofburgersrangingfrom0to100inincrementsof10.Aconcave-updecreasingcurve,labeled1,passesthroughpointA(10,45).Anotherconcave-updecreasingcurve,labeled2,passesthroughthepointsatB(20,40)andC(70,15).Anotherconcave-updecreasingcurve,labeled3,passesthroughthepointatE(40,30).Anotherconcave-updecreasingcurve,labeled4,passesthroughthepointatD(45,40).AtangentlabeledRisdrawnatpointB.AnothertangentlabeledTisdrawnatpointC.SolidlinesfromtheverticalaxisandhorizontalaxisconnectsplotE.DashedlinesfromtheverticalandhorizontalaxesconnectsplotAandC.Notethatthecoordinatevaluesareactualvalues.Returntoparent-slidecontainingimages.47Figure5.9DerivingaDemandCurve

-TextAlternativeReturntoparent-slidecontainingimages.PanelA:TheverticalaxisislabeledasthequantityofYrangingfrom0to100.ThehorizontalaxisislabeledasthequantityofXwithscales0,100,125,and200.Threedecreasingdiagonallinesaredrawn.Thefirstlinelabeledbudgetline1,PsubscriptXequals10dollars,startsat(0,100)andendsatC(100,0).Thesecondlinelabeledbudgetline2,PsubscriptXequals8dollars,startsat(0,100)andendsat(125,0).Thethirdlinelabeledbudgetline3,PsubscriptXequals5dollars,startsat(0,100)andendsat(200,0).Aconcave-updecreasingcurve,labeled1,touchesline1at(50,50).Anotherconcave-updecreasingcurve,labeled2,touchesline2at(65,50).Anotherconcave-updecreasingcurve,labeled3,touchesline3at(90,60).Notethatthecoordinatevaluesmentionedaboveareapproximate.PanelB:TheverticalaxisislabeledasthepriceofXindollarsrangingfrom0to10.ThehorizontalaxisislabeledasthequantityofXrangingfrom0to90.AlinelabeleddemandforXwithanegativeslopepassesthroughthepointsat(50,10),(65,8),and(90,5).Averticaldashedlinepassesthroughtheseplots.Notethattheabove-mentionedcoordinatevaluesareactualvalues.Returntoparent-slidecontainingimages.48Figure5.10DerivationofMarketDemand

-TextAlternativeReturntoparent-slidecontainingimages.Theverticalaxisislabeledaspriceandmarginalbenefitindollarsrangingfrom0to6inincrementsof1unit.Thehorizontalaxisislabeledasquantitydemandrangingfrom0to32inincrementsof4units.AcurvelabeledDsubscript1,beginsat(3,6),andpassesthroughthepointslabeledat(5,5),(8,4),(10,3),(12,2),andendsat(13,1).AnothercurvelabeledDsubscript2,beginsat(1,5),andpassesthroughthepointslabeledat(3,4),(5,3),(7,2),andendsat(10,1).AnothercurvelabeledDsubscript3,beginsat(1,4),andpassesthroughthepointslabeledat(4,3),(6,2),andendsat(8,1).AnothercurvelabeledDsubscriptMequalsMB,beginsat(3,6),andpassesthroughthepointslabeledat(6,5),A(12,4),(19,3),(25,2),andendsat(31,1).Notethatallthecoordinatevaluesareapproximate.AsolidlinefromtheverticalaxisandadashedlinefromthehorizontalaxisjoinpointAinthecurveDsubscriptMequalsMB.Returntoparent-slidecontainingimages.49Figure5.11CornerSolution:X*=0

-TextAlternativeReturntoparent-slidecontainingimages.TheverticalaxisislabeledasgoodYandthehorizontalaxisislabeledasgoodX.AlinewithanegativeslopeisdrawnfrompointAonthey-axistopointBonthex-axisformingaright-angledtriangle.AdashedlinewithanegativeslopebeginsatpointAonthey-axisandgoestotherighttopointZ.Fourconcave-updecreasingcurveslabeled1,2,3,and4aredrawn.Thecurvelabeled3startsfrompointAandgoesdowntotherightabovecurves1and2.Curve4liesabovecurve3andintersectsthelineAZatpointC.Returntoparent-slidecontainingimages.50Figure5.12TheSubstitutionEffectWhenPriceDecreases

-TextAlternativeReturntoparent-slidecontainingimages.TheverticalaxisislabeledasthequantityofYrangingfrom0to20.ThehorizontalaxisislabeledasthequantityofXrangingfrom0to25.AlinewithanegativeslopestartsatA(0,20)ontheverticalaxisandendsatpointB(10,0)onthehorizontalaxis.Anotherline,labeledtemporarybudgetline,withanegativeslopestartsatpointL(0,14)andendsatZ(17.5,0).AnotherlinewithanegativeslopestartsatpointA(0,20)andendsatD(25,0).Aconcave-updecreasingcurvelabeledIpassesthroughpointsE(3,14)andG(8,7).AverticaldashedlineisdrawnfrompointEtopointJ(3,0).AnotherverticaldashedlineisdrawnfrompointGtopointK(8,0).ThedistancebetweenthedashedverticallinesJandKislabeledthesubstitutioneffect.AnarrowfromthecurveIpointtothelineAD.AdashedarrownearpointDpointstonearpointZ.Notethatallabove-mentionedvaluesareapproximate.Returntoparent-slidecontainingimages.51Figure5.13SubstitutionandIncomeEffects:ADecreaseinPx

-TextAlternativeReturntoparent-slidecontainingimages.ThegraphistitledPanelA-normalgood.TheverticalaxisislabeledasthequantityofYrangingfrom0to20.ThehorizontalaxisislabeledasthequantityofXrangingfrom0to25.AlinewithanegativeslopestartsatA(0,20)andendsatpointB(10,0).AnotherlinewithanegativeslopestartsatpointL(014)andendsatZ(17.5,0).AnotherlinewithanegativeslopestartsatpointA(0,20)andendsatD(25,0).Aconcave-updecreasingcurvelabeled1passesthroughpointsE(3,14)andG(8,7).Anotherconcave-updecreasingcurvelabeled2passesthroughpointFat(12,11).ArightarrowislabeledIbetweenthedashedverticallineGKandthedashedverticallinedrawnfrompointFtoapoint(12,0).AnotherrightarrowislabeledSbetweenthedashedverticallineEJandthedashedverticallineGK.AnotherrightarrowislabeledTbetweenthedashedverticallineEJandthedashedverticallinedrawnfrompointFtoapoint(12,0).AnarrowfromlineABpointstolineAD.Notethatalltheabove-mentionedvaluesareapproximate.ThegraphistitledPanelB-inferiorgood.TheverticalaxisislabeledasthequantityofYrangingfrom0to20.ThehorizontalaxisislabeledasthequantityofXrangingfrom0to25.AlinewithanegativeslopestartsatA(0,20)andendsatpointB(10,0).AnotherlinewithanegativeslopestartsatpointL(0,14)andendsatZ(17.5,0).AnotherlinewithanegativeslopestartsatpointA(0,20)andendsatD(25,0).Aconcave-updecreasingcurvelabeled1passesthroughpointsE(3,14)andG(8,7).Anotherconcave-updecreasingcurvelabeled2passesthroughpointFat(6,16).AleftarrowislabeledIbetweenthedashedverticallineGKandthedashedverticallinedrawnfrompointFtoapoint(6,0).AnotherrightarrowislabeledSbetweenthedashedverticallineEJandthedashedverticallineGK.AnotherrightarrowislabeledTbetweenthedashedverticallineEJandthedashedverticallinedrawnfrompointFtoapoint(6,0).Notethatalltheabove-mentionedvaluesareapproximate.Returntoparent-slidecontainingimages.52