曼昆《经济学原理》英文版完整讲义丛elasticity

Copyright©2004South-Western5ElasticityandItsApplicationsCopyright©2004South-Western/ThomsonLearningElasticity...•…allowsustoanalyzesupplyanddemandwithgreaterprecision.•…isameasureofhowmuchbuyersandsellersrespondtochangesinmarketconditionsCopyright©2004South-Western/ThomsonLearningTHEELASTICITYOFDEMAND•Priceelasticityofdemandisameasureofhowmuchthequantitydemandedofagoodrespondstoachangeinthepriceofthatgood.•Priceelasticityofdemandisthepercentagechangeinquantitydemandedgivenapercentchangeintheprice.Copyright©2004South-Western/ThomsonLearningThePriceElasticityofDemandandItsDeterminants•AvailabilityofCloseSubstitutes•NecessitiesversusLuxuries•DefinitionoftheMarket•TimeHorizonCopyright©2004South-Western/ThomsonLearningThePriceElasticityofDemandandItsDeterminants•Demandtendstobemoreelastic:•thelargerthenumberofclosesubstitutes.•ifthegoodisaluxury.•themorenarrowlydefinedthemarket.•thelongerthetimeperiod.Copyright©2004South-Western/ThomsonLearningComputingthePriceElasticityofDemand•Thepriceelasticityofdemandiscomputedasthepercentagechangeinthequantitydemandeddividedbythepercentagechangeinprice.Priceelasticityofdemand=PercentagechangeinquantitydemandedPercentagechangeinpriceCopyright©2004South-Western/ThomsonLearning•Example:Ifthepriceofanicecreamconeincreasesfrom$2.00to$2.20andtheamountyoubuyfallsfrom10to8cones,thenyourelasticityofdemandwouldbecalculatedas:ComputingthePriceElasticityofDemandPriceelasticityofdemand=PercentagechangeinquantitydemandedPercentagechangeinprice()(..).1081010022020020010020%10%2Copyright©2004South-Western/ThomsonLearningTheMidpointMethod:ABetterWaytoCalculatePercentageChangesandElasticities•Themidpointformulaispreferablewhencalculatingthepriceelasticityofdemandbecauseitgivesthesameanswerregardlessofthedirectionofthechange.Priceelasticityofdemand=()/[()/]()/[()/]QQQQPPPP2121212122Copyright©2004South-Western/ThomsonLearningTheMidpointMethod:ABetterWaytoCalculatePercentageChangesandElasticities•Example:Ifthepriceofanicecreamconeincreasesfrom$2.00to$2.20andtheamountyoubuyfallsfrom10to8cones,thenyourelasticityofdemand,usingthemidpointformula,wouldbecalculatedas:()()/(..)(..)/..1081082220200200220222%95%232Copyright©2004South-Western/ThomsonLearningTheVarietyofDemandCurves•InelasticDemand•Quantitydemandeddoesnotrespondstronglytopricechanges.•Priceelasticityofdemandislessthanone.•ElasticDemand•Quantitydemandedrespondsstronglytochangesinprice.•Priceelasticityofdemandisgreaterthanone.Copyright©2004South-Western/ThomsonLearningComputingthePriceElasticityofDemandDemandispriceelastic$54DemandQuantity100050-3percent22-percent675.00)/2(4.005.00)-(4.0050)/2(10050)-(100EDPriceCopyright©2004South-Western/ThomsonLearningTheVarietyofDemandCurves•PerfectlyInelastic•Quantitydemandeddoesnotrespondtopricechanges.•PerfectlyElastic•Quantitydemandedchangesinfinitelywithanychangeinprice.•UnitElastic•Quantitydemandedchangesbythesamepercentageastheprice.Copyright©2004South-Western/ThomsonLearningTheVarietyofDemandCurves•Becausethepriceelasticityofdemandmeasureshowmuchquantitydemandedrespondstotheprice,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.Copyright©2004South-Western/ThomsonLearningTotalRevenueandthePriceElasticityofDemand•Totalrevenueistheamountpaidbybuyersandreceivedbysellersofagood.•Computedasthepriceofthegoodtimesthequantitysold.TR=PxQFigure2TotalRevenueCopyright©2003Southwestern/ThomsonLearningDemandQuantityQP0PriceP×Q=$400(revenue)$4100Copyright©2004South-Western/ThomsonLearningElasticityandTotalRevenuealongaLinearDemandCurve•Withaninelasticdemandcurve,anincreaseinpriceleadstoadecreaseinquantitythatisproportionatelysmaller.Thus,totalrevenueincreases.Figure3HowTotalRevenueChangesWhenPriceChanges:InelasticDemandCopyright©2003Southwestern/ThomsonLearningDemandQuantity0PriceRevenue=$100Quantity0PriceRevenue=$240Demand$1100$380AnIncreaseinpricefrom$1to$3……leadstoanIncreaseintotalrevenuefrom$100to$240Copyright©2004South-Western/ThomsonLearningElasticityandTotalRevenuealongaLinearDemandCurve•Withanelasticdemandcurve,anincr