管理经济学（第14版） 课件 第6章　弹性与需求

Chapter06ElasticityandDemandMANAGERIALECONOMICSFoundationsofBusinessAnalysisandStrategyFourteenthEditionCHRISTOPHERR.THOMAS©McGrawHillLLC.Allrightsreserved.NoreproductionordistributionwithoutthepriorwrittenconsentofMcGrawHillLLC.LearningObjectives6.1Definepriceelasticityofdemandanduseittopredictchangesinquantitydemandedandpriceofagood.6.2Explaintherolepriceelasticityplaysindetermininghowachangeinpriceaffectstotalrevenue.6.3Explainfactorsthataffectpriceelasticityofdemand.6.4Calculatepriceelasticityoveranintervalandatapointonademandcurve.6.5Relatemarginalrevenuetototalrevenueanddemandelasticityandwritethemarginalrevenueequationforlinearinversedemandfunctions.6.6Define/computeincomeelasticityofdemandandcross-priceelasticityofdemand.2PriceElasticityofDemand(E)Measuresresponsivenessorsensitivityofconsumerstochangesinthepriceofagood.PandQareinverselyrelatedbythelawofdemandsoEisalwaysnegative.ThelargertheabsolutevalueofE,themoresensitivebuyersaretoachangeinprice.3InterpretingPriceElasticityofDemandElastic:segmentofdemandforwhichInelastic:segmentofdemandforwhichUnitaryelastic:segmentofdemandforwhich4Table6.1PriceElasticityofDemand(E)ElasticityResponsivenessElasticUnitaryelasticInelasticNote.Thesymbol“||”denotestheabsolutevalue.5PriceElasticityandTotalRevenueTotalrevenueTotalamountpaidtoproducersforagoodorservice(TR=P×Q).PriceeffectTheeffectontotalrevenueofchangingprice,holdingoutputconstant.QuantityeffectTheeffectontotalrevenueofchangingoutput,holdingpriceconstant.6Table6.2RelationsBetweenPriceElasticityandTotalRevenueTableSummary:InthistableColumn2row1|%∆Q|>|%∆P|shouldbereadastheabsolutevalueofpercentdeltaQisgreaterthantheabsolutevalueofpercentdeltaP.column3row1|%∆Q|=|%∆P|shouldbereadastheabsolutevalueofpercentdeltaQequalstheabsolutevalueofpercentdeltaP.column4row1|%∆Q|<|%∆P|shouldbereadastheabsolutevalueofpercentdeltaQislessthantheabsolutevalueofpercentdeltaP.Elastic|%∆Q|>|%∆P|Q-EffectDominatesUnitaryElastic|%∆Q|=|%∆P|NoDominantEffectInelastic|%∆Q|<|%∆P|P-EffectDominatesPricerisesTRfallsNochangeinTRTRrisesPricefallsTRrisesNochangeinTRTRfalls7Figure6.1ChangesinTotalRevenueofBorderlineVideoEmporiumAccessthetextalternativeforslideimages.8FactorsAffectingPriceElasticityofDemandAvailabilityofsubstitutesThebetterandmorenumerousthesubstitutesforagood,themoreelasticisdemand.Percentageofconsumer’sbudgetThegreaterthepercentageoftheconsumer’sbudgetspentonthegood,themoreelasticisdemand.TimeperiodofadjustmentThelongerthetimeperiodconsumershavetoadjusttopricechange,themoreelasticisdemand.9CalculatingPriceElasticityofDemandPriceelasticitycanbecalculatedbymultiplyingtheslopeofdemand(ΔQ∕ΔP)bytheratioofpricedividedbyquantity(P∕Q)10ComputationofElasticityOveranIntervalPriceelasticitycanbemeasuredataninterval(orarc)alongdemandorataspecificpointonthedemandcurve.Ifthepricechangeisrelativelysmall,apointcalculationissuitable.Ifthepricechangespansasizablearcalongthedemandcurve,theintervalcalculationprovidesabettermeasure.Whencalculatingpriceelasticityofdemandoveranintervalofdemand,usetheintervalorarcelasticityformula:11ComputationofElasticityataPointPointelasticityisameasurementofdemandelasticitycalculatedatapointonademandcurveratherthanoveraninterval.Whencalculatingpriceelasticityatapointondemand,multiplytheslopeofdemand(ΔQ∕ΔP),computedatthepointofmeasure,timestheratioP∕Q,usingthevaluesofPandQatthepointofmeasure.Methodofmeasuringpointelasticitydependsonwhetherdemandislinearorcurvilinear.12PointElasticityWhenDemandIsLinearGivenQ=a+bP+cM+dPR,letincomeandpriceoftherelatedgoodtakespecificvaluesandrespectively.ThenshowdemandasQ=a′+bP,

whereandtheslopeparameterisb=ΔQ∕ΔPComputeelasticityusingeitherofthetwoformulasbelowwhichgivethesamevalueforEwherePandQarevaluesofpriceandquantitydemandedatthepointofmeasurealongdemand,andA(=−a′∕

b)istheprice-interceptofdemand.13PointElasticityWhenDemandIsCurvilinearComputeelasticityusingeitheroftwoequivalentformulasbelow:whereΔQ∕ΔPistheslopeofthecurveddemandatthepointofmeasure,PandQarevaluesofpriceandquantitydemandedatthepointofmeasure,andAisthepriceinterceptofthetangentlineextendedtocrossthepriceaxis.14Figure6.2CalculatingPointElasticityforCurvilinearDemandAccessthetextalternativeforslideimages.15Elasticity(Generally)VariesAlongaDemandCurveForlineardemand,priceandvarydirectly.Thehighertheprice,themoreelasticisdemand.Thelowertheprice,thelesselasticisdemand.Forcurvilineardemand,thereisnogeneralruleabouttherelationbetweenprice,quantity.Specialcaseofwhichhasaconstantpriceelasticity(equaltob)forallprices.16Figure6.3ConstantElasticityofDemandAccessthetextalternativeforslideimages.17MarginalRevenueMarginalrevenue(MR)istheadditiontototalrevenueattributabletosellingoneadditionalunitofoutput.SinceMRmeasurestherateofchangeintotalrevenueasquantitychanges,MRistheslopeofthetotalrevenue(TR)curve:Inframarginalunitsareunitsofoutputthatcouldhavebeensoldatahigherpricehadafirmnotlowereditspricetosellthemarginalunit.18Table6.3DemandandMarginalRevenue(1)(2)(3)(4)UnitSalesPriceTotalRevenueMarginalRevenue(ΔTR∕ΔQ)0$4.50$0–14.004.00$4.0023.507.003.0033.109.302.3042.8011.201.9052.4012.000.8062.0012.00071.5010.50−1.5019Figure6.4Demand,MarginalRevenue,andTotalRevenueAccessthetextalternativeforslideimages.20DemandandMarginalRevenueWheninversedemandislinear:P=A+BQ(A>0,B<0)Marginalrevenueisalsolinear,intersectsthevertical(price)axisatthesamepointasdemand,andistwiceassteepasdemand:MR=A+2BQ21Figure6.5LinearDemand,MarginalRevenue,andElasticity(Q=120−20P)Accessthetextalternativeforslideimages.22Table6.4MarginalRevenue,TotalRevenue,andPriceElasticityofDemand(1)MarginalRevenue(2)TotalRevenue(3)PriceElasticityofDemandMR>0TRincreasesasQincreases(Pdecreases)ElasticMR=0TRismaximizedUnitelasticMR<0TRdecreasesasQincreases(Pdecreases)Inelastic23MarginalRevenueandPriceElasticityForalldemandandmarginalrevenuecurves,therelationbetweenmarginalrevenue,price,andelasticitycanbeexpressedas:24IncomeElasticityIncomeelasticity(EM)measurestheresponsivenessofquantitydemandedtochangesinincome,holdingthepriceofthegoodandallotherdemanddeterminantsconstant.Positiveforanormalgood.Negativeforaninferiorgood.25Figure6.6CalculatingIncomeElasticityofDemandAccessthetextalternativeforslideimages.26Cross-PriceElasticityCross-priceelasticity(EXR)measurestheresponsivenessofquantitydemandedofgoodXtochangesinthepriceofrelatedgoodR,holdingthepriceofgoodXandallotherdemanddeterminantsforgoodXconstant.Positivewhenthetwogoodsaresubstitutes.Negativewhenthetwogoodsarecomplements.27IntervalElasticityMeasuresTocalculateintervalmeasuresofincomeandcross-priceelasticities,thefollowingformulascanbeused:28PointElasticityMeasuresForthelineardemandfunctionQ=a+bP+cM+dPR,pointmeasuresofincomeandcross-priceelasticitiescanbecalculatedas:29Summary1Priceelasticityofdemand,E,measuresresponsivenessorsensitivityofconsumerstochangesinthepriceofagood:ThelargertheabsolutevalueofE,themoresensitivebuyerswillbetoachangeinprice.Theeffectofchangingpriceontotalrevenueisdeterminedbythepriceelasticityofdemand.Whendemandiselastic(inelastic),thequantity(price)effectdominates.Severalfactorsaffecttheelasticityofdemand:Availabilityofsubstitutesforagood.Percentageoftheconsumers’budgetsspentonthegood.Lengthoftimeconsumershavetoadjusttopricechanges.30Summary2Whendemandislinear,thepointelasticitycanbecomputedas:WhenMRispositive(negative),totalrevenueincreases(decreases)asquantityincreases,anddemandiselastic(inelastic).WhenMRis0,thepriceelasticityofdemandisunitaryandtotalrevenueismaximized.Foranydemandcurve,whendemandiselastic(inelastic),MRispositive(negative).Whendemandisunitaryelastic,MRis0.Incomeelasticity,EM,measurestheresponsivenessofquantitydemandedtoincomechanges,allelseconstant.Cross-priceelasticity,EXY,measurestheresponsivenessofquantitydemandedofgoodXtochangesinthepriceofgoodY,allelseconstant.31EndofMainContent©McGrawHillLLC.Allrightsreserved.NoreproductionordistributionwithoutthepriorwrittenconsentofMcGrawHillLLC.AccessibilityContent:TextAlternativesforImages33Figure6.1ChangesinTotalRevenueofBorderlineVideoEmporium-TextAlternativeReturntoparent-slidecontainingimages.ThegraphistitledpanelA-anelasticregionofdemandexplainingquantityeffectdominates.TheverticalaxisislabeledaspriceperDVD(dollars)rangingfrom0to24.ThehorizontalaxisislabeledasthenumberofDVDsperweekrangingfrom0to2,400.Alinewithanegativeslope,labeledD,startsat(0,24),passesthroughthepointsa(600,18),b(800,16),f(1,100,13),g(1,300,11)andendsat(2,400,0).ThedistancebetweenpointsaandbislabeledEequalsnegative2.43.Notethatalltheabove-mentionedcoordinatesareactualvalues.ThegraphistitledpanelB-aninelasticregionofdemandexplainingpriceeffectdominates.TheverticalaxisislabeledaspriceperDVD(dollars)rangingfrom0to24.ThehorizontalaxisislabeledasthequantityofDVDsperweekrangingfrom0to2,400.Alinewithanegativeslope,labeledD,startsat(0,24),passesthroughthepointsa(600,18),b(800,16),c(1,500,9),d(1,700,7)andendsat(2,400,0).ThedistancebetweenpointsaandbislabeledEequalsnegative0.50.Notethatalltheabove-mentionedcoordinatesareactualvalues.Returntoparent-slidecontainingimages.34Figure6.2CalculatingPointElasticityforCurvilinearDemand

-TextAlternativeReturntoparent-slidecontainingimages.Theverticalaxisislabeledasprice(dollars)rangingfrom0to140.Thehorizontalaxisislabeledasaquantityrangingfrom0to105.Aconcave-updecreasingcurve,labeledD,passesthroughthepointsR(30,100)andS(105,40).AtangentRTisdrawnatpointRonthecurve.AnothertangentSTprimeisdrawnatpointSonthecurve.PointRislabeledEsubscriptRequalsnegative2.5.PointSislabeledEsubscriptSequalsnegative0.8.Notethatalltheabove-mentionedcoordinatesareactualvalues.Returntoparent-slidecontainingimages.35Figure6.3ConstantElasticityofDemand

-TextAlternativeReturntoparent-slidecontainingimages.Theverticalaxisislabeledasprice(dollars)rangingfrom0to80inincrementsof20.Thehorizontalaxisislabeledasaquantityrangingfrom0to3,000inincrementsof1,000.Aconcave-updecreasingcurve,labeledD:Qequals100,000timesPtothepowernegative1.5,passesthroughthepointsV(500,40)andU(1,100,20).AtangentlineisdrawnatpointVonthecurve.AnothertangentlineisdrawnatpointUonthecurve.PointVislabeledEsubscriptVequalsnegative1.5.PointUislabeledEsubscriptUequalsnegative1.5.Notethatthevaluesmentionedaboveareapproximate.Returntoparent-slidecontainingimages.36Figure6.4Demand,MarginalRevenue,andTotalRevenue

-TextAlternativeReturntoparent-slidecontainingimages.ThegraphistitledpanelA.Theverticalaxisislabeledaspriceandmarginalrevenue(dollars)rangingfromnegative1.50to4.00inincrementsof0.50.Thehorizontalaxisislabeledasaquantityrangingfrom0to7inincrementsof1.AcurvelabeledDbeginsat(1,4.00),andpassesthroughthepointslabeledat(2,3.50),(3,3.10),(4,2.80),(5,2.40),(6,2.00),and(7,1.50).AnothercurvelabeledMR,beginsat(1,4.00),andpassesthroughthepointslabeledat(2,3.00),(3,2.30),(4,1.90),(5,0.80),(6,0),and(7,negative1.50).Notethatalltheabove-mentionedcoordinatesareactualvalues.ThegraphistitledpanelB.Theverticalaxisislabeledastotalrevenue(dollars)rangingfrom0to12.00inincrementsof2.00.Thehorizontalaxisislabeledasaquantityrangingfrom0to7inincrementsof1.AcurvelabeledTRbeginsat(0,0),andpassesthroughthepointslabeledat(1,4.00),(2,7.00),(3,9.30),(4,11.20),(5,12.00),(6,12.00),and(7,10.50).Notethatalltheabove-mentionedcoordinatesareactualvalues.Returntoparent-slidecontainingimages.37Figure6.5LinearDemand,MarginalRevenue,andElasticity(Q=120−20P)

-TextAlternativeReturntoparent-slidecontainingimages.ThegraphistitledpanelA.Theverticalaxisislabeledaspriceandmarginalrevenue(dollars)rangingfrom0to6inincrementsof2.Thehorizontalaxisislabeledasthequantityrangingfrom0to120.Aline,labeledMRequals6minus0.10timesQ,withnegativeslopestartsat(0,6),passesthroughthepoint(40,2),andendsat(60,0).Anotherline,labeledinverseD:Pequals6minus0.05timesQ,withnegativeslopestartsat(0,6),passesthroughthepointsat(40,4),(60,3),andendsat(120,0).Thepointat(60,3)islabeledmodulusofEequals1.Thedistancebetweenpointsat(0,6)and(60,3)islabeledmodulusofEgreaterthan1.Thedistancebetweenpointsat(60,3)and(120,0)islabeledmodulusofElessthan1.Notethatalltheabove-mentionedcoordinatesareactualvalues.ThegraphistitledpanelB.Theverticalaxisislabeledastotalrevenue(dollars)rangingfrom0to180.Thehorizontalaxisislabeledasthequantityrangingfrom0to120.AcurvelabeledTotalrevenue,TRequalsPtimesQequals6Qminus0.05Qsquared,isconcavedown,beginsattheorigin,riseslefttoright,reachestohighpointat(60,180),thenfallslefttothe