Chap_05弹性及其应用(经济学原理,曼昆,中英文双语)

ElasticityandItsApplication弹性及其应用Chapter5Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.Elasticity...弹性…u…isameasureofhowmuchbuyersandsellersrespondtochangesinmarketconditions.…是衡量买者和卖者对市场条件变动的反应大小的指标。u…allowsustoanalyzesupplyanddemandwithgreaterprecision.…使我们可以更精确地分析供给与需求Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.PriceElasticityofDemanduPriceelasticityofdemandisthepercentagechangeinquantitydemandedgivenapercentchangeintheprice.uItisameasureofhowmuchthequantitydemandedofagoodrespondstoachangeinthepriceofthatgood.Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.需求的价格弹性u需求的价格弹性——价格变化1%引起的需求量的变化百分比值。u它是一种物品的需求量对其价格变动的反应程度的衡量。Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.DeterminantsofPriceElasticityofDemand需求价格弹性的决定因素uNecessitiesversusLuxuries必需品与奢侈品uAvailabilityofCloseSubstitutes相近替代品的可获得性uDefinitionoftheMarket市场的定义uTimeHorizon时间的长短Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.DeterminantsofPriceElasticityofDemandDemandtendstobemoreelastic:uifthegoodisaluxury.uthelongerthetimeperiod.uthelargerthenumberofclosesubstitutes.uthemorenarrowlydefinedthemarket.Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.价格需求弹性的决定因素需求倾向于富有弹性：u如果物品是奢侈品u时期更长u相近替代品的数量更多u市场定义的范围更窄Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.ComputingthePriceElasticityofDemandThepriceelasticityofdemandiscomputedasthepercentagechangeinthequantitydemandeddividedbythepercentagechangeinprice.PriceElasticityofDemand=PercentageChangeinQuantityDemandedPercentageChangeinPricePriceElasticityofDemand=PercentageChangeinQuantityDemandedPercentageChangeinPriceHarcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.计算需求价格弹性用需求量变动的百分比除以价格变动的百分比来计算需求价格弹性。=需求量变动的百分比需求价格弹性价格变动的百分比Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.ComputingthePriceElasticityofDemandpriceinchangePercentagedemandedquatityinchangePercentagedemandofelasticityPriceExample:Ifthepriceofanicecreamconeincreasesfrom$2.00to$2.20andtheamountyoubuyfallsfrom10to8conesthenyourelasticityofdemandwouldbecalculatedas:2percent10percent2010000200220210010810.)..()(Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.计算需求价格弹性需求量变动的百分比需求价格弹性价格变动的百分比例子:如果冰激凌蛋卷的价格从2美元上升到2.2美元，你的购买量从10个下降到8个，你的需求价格弹性计算如下：(108)10020102(2.202.00)101002.00％％Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.TheMidpointMethod:ABetterWaytoCalculatePercentageChangesandElasticitiesThemidpointformulaispreferablewhencalculatingthepriceelasticityofdemandbecauseitgivesthesameanswerregardlessofthedirectionofthechange.)/2]P)/[(PP(P)/2]Q)/[(QQ(Q=DemandofElasticityPrice12121212Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.中点法:一种计算百分比变化和弹性的更好方法中点法是计算需求价格弹性的更好方法，因为无论变动的方向如何，中点法给出了同一个答案。21212121(QQ)/[(QQ)/2]=(PP)/[(PP)/2]需求价格弹性Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.TheMidpointMethod:ABetterWaytoCalculatePercentageChangesandElasticitiesExample:Ifthepriceofanicecreamconeincreasesfrom$2.00to$2.20andtheamountyoubuyfallsfrom10to8conestheyourelasticityofdemand,usingthemidpointformula,wouldbecalculatedas:32.25.9222/)20.200.2()00.220.2(2/)810()810(percentpercent)/2]P)/[(PP(P)/2]Q)/[(QQ(Q=DemandofElasticityPrice12121212Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.中点法:一种计算百分比变化和弹性的更好方法例子:如果冰激凌蛋卷的价格从2美元上升到2.2美元，你的购买量从10个下降到8个，利用中点法你的需求价格弹性计算如下：(108)22(108)/22.32(2.202.00)9.5(2.002.20)/2％％21212121(QQ)/[(QQ)/2]=(PP)/[(PP)/2]需求价格弹性Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.TheVarietyofDemandCurvesInelasticDemanduQuantitydemandeddoesnotrespondstronglytopricechanges.uPriceelasticityofdemandislessthanone.ElasticDemanduQuantitydemandedrespondsstronglytochangesinprice.uPriceelasticityofdemandisgreaterthanone.Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.多种需求曲线缺乏弹性的需求u需求量不随着价格变化而强烈变化。u需求价格弹性小于1。富有弹性的需求u需求量随着价格变化而强烈变化。u需求价格弹性大于1。Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.ComputingthePriceElasticityofDemand计算需求的价格弹性Demandispriceelastic需求富有弹性$54Demand需求Quantity数量1000Price价格50D(100-50)(10050)/2E(4.00-5.00)(4.005.00)/267-3-22％％Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.TheVarietyofDemandCurvesuPerfectlyInelasticQuantitydemandeddoesnotrespondtopricechanges.uPerfectlyElasticQuantitydemandedchangesinfinitelywithanychangeinprice.uUnitElasticQuantitydemandedchangesbythesamepercentageastheprice.Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.多种需求曲线u完全无弹性需求量不随价格变化而变化。u完全弹性价格极小变化引起需求量极大变动。u单位弹性需求量与价格同比例变动。Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.AVarietyofDemandCurves多种需求弹性曲线Becausethepriceelasticityofdemandmeasureshowmuchquantitydemandedrespondstotheprice,itiscloselyrelatedtotheslopeofthedemandcurve.由于需求的价格弹性衡量需求量对价格变化的反应程度，所以它与需求曲线的斜率密切相关。Harcourt,Inc.itemsandderiveditemscopyright©2001byHarcourt,Inc.PerfectlyInelasticDemand—Elasticityequals0完全无弹性的需求——弹性等于0Quantity数量Price价格4$5Demand需求1002....leavesthequantitydemandedunchanged.2