曼昆《经济学原理》英文版完整讲义丛elasticity课件

5ElasticityandItsApplicationsElasticity... …allowsustoanalyzesupplyanddemandwithgreaterprecision.…isameasureofhowmuchbuyersandsellersrespondtochangesinmarketconditions

THEELASTICITYOFDEMANDPriceelasticityofdemandisameasureofhowmuchthequantitydemandedofagoodrespondstoachangeinthepriceofthatgood.Priceelasticityofdemandisthepercentagechangeinquantitydemandedgivenapercentchangeintheprice.

ThePriceElasticityofDemandandItsDeterminantsAvailabilityofCloseSubstitutesNecessitiesversusLuxuriesDefinitionoftheMarketTimeHorizonThePriceElasticityofDemandandItsDeterminantsDemandtendstobemoreelastic:thelargerthenumberofclosesubstitutes.ifthegoodisaluxury.themorenarrowlydefinedthemarket.thelongerthetimeperiod.ComputingthePriceElasticityofDemandThepriceelasticityofdemandiscomputedasthepercentagechangeinthequantitydemandeddividedbythepercentagechangeinprice.Example:Ifthepriceofanicecreamconeincreasesfrom$2.00to$2.20andtheamountyoubuyfallsfrom10to8cones,thenyourelasticityofdemandwouldbecalculatedas:ComputingthePriceElasticityofDemandTheMidpointMethod:ABetterWaytoCalculatePercentageChangesandElasticitiesThemidpointformulaispreferablewhencalculatingthepriceelasticityofdemandbecauseitgivesthesameanswerregardlessofthedirectionofthechange.TheMidpointMethod:ABetterWaytoCalculatePercentageChangesandElasticitiesExample:Ifthepriceofanicecreamconeincreasesfrom$2.00to$2.20andtheamountyoubuyfallsfrom10to8cones,thenyourelasticityofdemand,usingthemidpointformula,wouldbecalculatedas:TheVarietyofDemandCurvesInelasticDemandQuantitydemandeddoesnotrespondstronglytopricechanges.Priceelasticityofdemandislessthanone.ElasticDemandQuantitydemandedrespondsstronglytochangesinprice.Priceelasticityofdemandisgreaterthanone.ComputingthePriceElasticityofDemandDemandispriceelastic$54DemandQuantity100050PriceTheVarietyofDemandCurvesPerfectlyInelasticQuantitydemandeddoesnotrespondtopricechanges.PerfectlyElasticQuantitydemandedchangesinfinitelywithanychangeinprice.UnitElasticQuantitydemandedchangesbythesamepercentageastheprice.TheVarietyofDemandCurvesBecausethepriceelasticityofdemandmeasureshowmuchquantitydemandedrespondstotheprice,itiscloselyrelatedtotheslopeofthedemandcurve.Figure1ThePriceElasticityofDemandCopyright©2003Southwestern/ThomsonLearning(a)PerfectlyInelasticDemand:ElasticityEquals0$54QuantityDemand10001.Anincreaseinprice...2....leavesthequantitydemandedunchanged.PriceFigure1ThePriceElasticityofDemand(b)InelasticDemand:ElasticityIsLessThan1Quantity0$590Demand1.A22%increaseinprice...Price2....leadstoan11%decreaseinquantitydemanded.4100Figure1ThePriceElasticityofDemandCopyright©2003Southwestern/ThomsonLearning2....leadstoa22%decreaseinquantitydemanded.(c)UnitElasticDemand:ElasticityEquals1Quantity41000Price$5801.A22%increaseinprice...DemandFigure1ThePriceElasticityofDemand(d)ElasticDemand:ElasticityIsGreaterThan1DemandQuantity41000Price$5501.A22%increaseinprice...2....leadstoa67%decreaseinquantitydemanded.Figure1ThePriceElasticityofDemand(e)PerfectlyElasticDemand:ElasticityEqualsInfinityQuantity0Price$4Demand2.Atexactly$4,consumerswillbuyanyquantity.1.Atanypriceabove$4,quantitydemandediszero.3.Atapricebelow$4,quantitydemandedisinfinite.TotalRevenueandthePriceElasticityofDemandTotalrevenueistheamountpaidbybuyersandreceivedbysellersofagood.Computedasthepriceofthegoodtimesthequantitysold.

TR=PxQFigure2TotalRevenueCopyright©2003Southwestern/ThomsonLearningDemandQuantityQP0Price

P×Q=$400(revenue)$4100ElasticityandTotalRevenuealongaLinearDemandCurveWithaninelasticdemandcurve,anincreaseinpriceleadstoadecreaseinquantitythatisproportionatelysmaller.Thus,totalrevenueincreases.Figure3HowTotalRevenueChangesWhenPriceChanges:InelasticDemandCopyright©2003Southwestern/ThomsonLearningDemandQuantity0PriceRevenue=$100Quantity0PriceRevenue=$240Demand$1100$380AnIncreaseinpricefrom$1to$3……leadstoanIncreaseintotalrevenuefrom$100to$240ElasticityandTotalRevenuealongaLinearDemandCurveWithanelasticdemandcurve,anincreaseinthepriceleadstoadecreaseinquantitydemandedthatisproportionatelylarger.Thus,totalrevenuedecreases.Figure4HowTotalRevenueChangesWhenPriceChanges:ElasticDemandCopyright©2003Southwestern/ThomsonLearningDemandQuantity0PriceRevenue=$200$450DemandQuantity0PriceRevenue=$100$520AnIncreaseinpricefrom$4to$5……leadstoandecreaseintotalrevenuefrom$200to$100ElasticityofaLinearDemandCurveIncomeElasticityofDemandIncomeelasticityofdemandmeasureshowmuchthequantitydemandedofagoodrespondstoachangeinconsumers’income.Itiscomputedasthepercentagechangeinthequantitydemandeddividedbythepercentagechangeinincome.

ComputingIncomeElasticityIncomeElasticityTypesofGoodsNormalGoodsInferiorGoodsHigherincomeraisesthequantitydemandedfornormalgoodsbutlowersthequantitydemandedforinferiorgoods.IncomeElasticityGoodsconsumersregardasnecessitiestendtobeincomeinelasticExamplesincludefood,fuel,clothing,utilities,andmedicalservices.Goodsconsumersregardasluxuriestendtobeincomeelastic.Examplesincludesportscars,furs,andexpensivefoods.THEELASTICITYOFSUPPLYPriceelasticityofsupplyisameasureofhowmuchthequantitysuppliedofagoodrespondstoachangeinthepriceofthatgood.Priceelasticityofsupplyisthepercentagechangeinquantitysuppliedresultingfromapercentchangeinprice.Figure6ThePriceElasticityofSupplyCopyright©2003Southwestern/ThomsonLearning(a)PerfectlyInelasticSupply:ElasticityEquals0$54SupplyQuantity10001.Anincreaseinprice...2....leavesthequantitysuppliedunchanged.PriceFigure6ThePriceElasticityofSupplyCopyright©2003Southwestern/ThomsonLearning(b)InelasticSupply:ElasticityIsLessThan1110$51004Quantity01.A22%increaseinprice...Price2....leadstoa10%increaseinquantitysupplied.SupplyFigure6ThePriceElasticityofSupplyCopyright©2003Southwestern/ThomsonLearning(c)UnitElasticSupply:ElasticityEquals1125$51004Quantity0Price2....leadstoa22%increaseinquantitysupplied.1.A22%increaseinprice...SupplyFigure6ThePriceElasticityofSupplyCopyright©2003Southwestern/ThomsonLearning(d)ElasticSupply:ElasticityIsGreaterThan1Quantity0Price1.A22%increaseinprice...2....leadstoa67%increaseinquantitysupplied.4100$5200SupplyFigure6ThePriceElasticityofSupplyCopyright©2003Southwestern/ThomsonLearning(e)PerfectlyElasticSupply:ElasticityEqualsInfinityQuantity0Price$4Supply3.Atapricebelow$4,quantitysuppliediszero.2.Atexactly$4,producerswillsupplyanyquantity.1.Atanypriceabove$4,quantitysuppliedisinfinite.DeterminantsofElasticityofSupplyAbilityofsellerstochangetheamountofthegoodtheyproduce.Beach-frontlandisinelastic.Books,cars,ormanufacturedgoodsareelastic.Timeperiod.Supplyismoreelasticinthelongrun.ComputingthePriceElasticityofSupplyThepriceelasticityofsupplyiscomputedasthepercentagechangeinthequantitysupplieddividedbythepercentagechangeinprice.THREEAPPLICATIONSOFSUPPLY,DEMAND,ANDELASTICITYCangoodnewsforfarmingbebadnewsforfarmers?Whathappenstowheatfarmersandthemarketforwheatwhenuniversityagronomistsdiscoveranewwheathybridthatismoreproductivethanexistingvarieties?THREEAPPLICATIONSOFSUPPLY,DEMAND,ANDELASTICITYExaminewhetherthesupplyordemandcurveshifts.Determinethedirectionoftheshiftofthecurve.Usethesupply-and-demanddiagramtoseehowthemarketequilibriumchanges.Figure8AnIncreaseinSupplyintheMarketforWheatCopyright©2003Southwestern/ThomsonLearningQuantityofWheat0PriceofWheat3....andaproportionatelysmallerincreaseinquantitysold.Asaresult,revenuefallsfrom$300to$220.DemandS1S22....leadstoalargefallinprice...

1.Whendemandisinelastic,anincreaseinsupply...2110$3100ComputethePriceElasticityofSupplySupplyisinelasticSummaryPriceelasticityofdemandmeas