曼昆经济学原理第五章.ppt

5 ElasticityandItsApplications Elasticity allowsustoanalyzesupplyanddemandwithgreaterprecision isameasureofhowmuchbuyersandsellersrespondtochangesinmarketconditions THEELASTICITYOFDEMAND Priceelasticityofdemandisameasureofhowmuchthequantitydemandedofagoodrespondstoachangeinthepriceofthatgood Priceelasticityofdemandisthepercentagechangeinquantitydemandedgivenapercentchangeintheprice ThePriceElasticityofDemandandItsDeterminants AvailabilityofCloseSubstitutesNecessitiesversusLuxuriesDefinitionoftheMarketTimeHorizon ThePriceElasticityofDemandandItsDeterminants Demandtendstobemoreelastic thelargerthenumberofclosesubstitutes ifthegoodisaluxury themorenarrowlydefinedthemarket thelongerthetimeperiod ComputingthePriceElasticityofDemand Thepriceelasticityofdemandiscomputedasthepercentagechangeinthequantitydemandeddividedbythepercentagechangeinprice Example Ifthepriceofanicecreamconeincreasesfrom 2 00to 2 20andtheamountyoubuyfallsfrom10to8cones thenyourelasticityofdemandwouldbecalculatedas ComputingthePriceElasticityofDemand TheMidpointMethod ABetterWaytoCalculatePercentageChangesandElasticities Themidpointformulaispreferablewhencalculatingthepriceelasticityofdemandbecauseitgivesthesameanswerregardlessofthedirectionofthechange TheMidpointMethod ABetterWaytoCalculatePercentageChangesandElasticities Example Ifthepriceofanicecreamconeincreasesfrom 2 00to 2 20andtheamountyoubuyfallsfrom10to8cones thenyourelasticityofdemand usingthemidpointformula wouldbecalculatedas TheVarietyofDemandCurves InelasticDemandQuantitydemandeddoesnotrespondstronglytopricechanges Priceelasticityofdemandislessthanone ElasticDemandQuantitydemandedrespondsstronglytochangesinprice Priceelasticityofdemandisgreaterthanone ComputingthePriceElasticityofDemand Demandispriceelastic 5 4 Demand Quantity 100 0 50 Price TheVarietyofDemandCurves PerfectlyInelasticQuantitydemandeddoesnotrespondtopricechanges PerfectlyElasticQuantitydemandedchangesinfinitelywithanychangeinprice UnitElasticQuantitydemandedchangesbythesamepercentageastheprice TheVarietyofDemandCurves Becausethepriceelasticityofdemandmeasureshowmuchquantitydemandedrespondstotheprice itiscloselyrelatedtotheslopeofthedemandcurve Figure1ThePriceElasticityofDemand Copyright 2003Southwestern ThomsonLearning a PerfectlyInelasticDemand ElasticityEquals0 Quantity 0 Price Figure1ThePriceElasticityofDemand b InelasticDemand ElasticityIsLessThan1 Quantity 0 Price Figure1ThePriceElasticityofDemand Copyright 2003Southwestern ThomsonLearning c UnitElasticDemand ElasticityEquals1 Quantity 0 Price Figure1ThePriceElasticityofDemand d ElasticDemand ElasticityIsGreaterThan1 Quantity 0 Price Figure1ThePriceElasticityofDemand e PerfectlyElasticDemand ElasticityEqualsInfinity Quantity 0 Price TotalRevenueandthePriceElasticityofDemand Totalrevenueistheamountpaidbybuyersandreceivedbysellersofagood Computedasthepriceofthegoodtimesthequantitysold TR PxQ Figure2TotalRevenue Copyright 2003Southwestern ThomsonLearning Quantity 0 Price ElasticityandTotalRevenuealongaLinearDemandCurve Withaninelasticdemandcurve anincreaseinpriceleadstoadecreaseinquantitythatisproportionatelysmaller Thus totalrevenueincreases Figure3HowTotalRevenueChangesWhenPriceChanges InelasticDemand Copyright 2003Southwestern ThomsonLearning Quantity 0 Price Quantity 0 Price AnIncreaseinpricefrom 1to 3 leadstoanIncreaseintotalrevenuefrom 100to 240 ElasticityandTotalRevenuealongaLinearDemandCurve Withanelasticdemandcurve anincreaseinthepriceleadstoadecreaseinquantitydemandedthatisproportionatelylarger Thus totalrevenuedecreases Figure4HowTotalRevenueChangesWhenPriceChanges ElasticDemand Copyright 2003Southwestern ThomsonLearning Quantity 0 Price Quantity 0 Price AnIncreaseinpricefrom 4to 5 leadstoandecreaseintotalrevenuefrom 200to 100 ElasticityofaLinearDemandCurve IncomeElasticityofDemand Incomeelasticityofdemandmeasureshowmuchthequantitydemandedofagoodrespondstoachangeinconsumers income Itiscomputedasthepercentagechangeinthequantitydemandeddividedbythepercentagechangeinincome ComputingIncomeElasticity IncomeElasticity TypesofGoodsNormalGoodsInferiorGoodsHigherincomeraisesthequantitydemandedfornormalgoodsbutlowersthequantitydemandedforinferiorgoods IncomeElasticity GoodsconsumersregardasnecessitiestendtobeincomeinelasticExamplesincludefood fuel clothing utilities andmedicalservices Goodsconsumersregardasluxuriestendtobeincomeelastic Examplesincludesportscars furs andexpensivefoods THEELASTICITYOFSUPPLY Priceelasticityofsupplyisameasureofhowmuchthequantitysuppliedofagoodrespondstoachangeinthepriceofthatgood Priceelasticityofsupplyisthepercentagechangeinquantitysuppliedresultingfromapercentchangeinprice Figure6ThePriceElasticityofSupply Copyright 2003Southwestern ThomsonLearning a PerfectlyInelasticSupply ElasticityEquals0 Quantity 100 0 Price Figure6ThePriceElasticityofSupply Copyright 2003Southwestern ThomsonLearning b InelasticSupply ElasticityIsLessThan1 Quantity 0 Price Figure6ThePriceElasticityofSupply Copyright 2003Southwestern ThomsonLearning c UnitElasticSupply ElasticityEquals1 Quantity 0 Price Figure6ThePriceElasticityofSupply Copyright 2003Southwestern ThomsonLearning d ElasticSupply ElasticityIsGreaterThan1 Quantity 0 Price Figure6ThePriceElasticityofSupply Copyright 2003Southwestern ThomsonLearning e PerfectlyElasticSupply ElasticityEqualsInfinity Quantity 0 Price DeterminantsofElasticityofSupply Abilityofsellerstochangetheamountofthegoodtheyproduce Beach frontlandisinelastic Books cars ormanufacturedgoodsareelastic Timeperiod Supplyismoreelasticinthelongrun ComputingthePriceElasticityofSupply Thepriceelasticityofsupplyiscomputedasthepercentagechangeinthequantitysupplieddividedbythepercentagechangeinprice THREEAPPLICATIONSOFSUPPLY DEMAND ANDELASTICITY Cangoodnewsforfarmingbebadnewsforfarmers Whathappenstowheatfarmersandthemarketforwheatwhenuniversityagronomistsdiscoveranewwheathybridthatismoreproductivethanexistingvarieties THREEAPPLICATIONSOFSUPPLY DEMAND ANDELASTICITY Examinewhetherthesupplyordemandcurveshifts Determinethedirectionoftheshiftofthecurve Usethesupply and demanddiagramtoseehowthemarketequilibriumchanges Figure8AnIncreaseinSupplyintheMarketforWheat Copyright 2003Southwestern ThomsonLearning Quantityof Wheat 0 Priceof Wheat ComputethePriceElasticityofSupply Supplyisinelastic Summary Priceelasticityofdemandmeasureshowmuchthequantitydemandedrespondstochangesintheprice Priceelasticityofdemandiscalculatedasthepercentagechange