经济学第四章ppt课件.ppt

ElasticityanditsApplication 5 弹性及其应用 Inthischapter lookfortheanswerstothesequestions Whatiselasticity Whatkindsofissuescanelasticityhelpusunderstand Whatisthepriceelasticityofdemand Howisitrelatedtothedemandcurve Howisitrelatedtorevenue expenditure Whatisthepriceelasticityofsupply Howisitrelatedtothesupplycurve Whataretheincomeandcross priceelasticitiesofdemand 什么是弹性 弹性能帮助我们理解什么问题 什么是需求价格弹性 它与需求曲线有什么联系 它与收益与支出又有什么联系 什么是供给价格弹性 它与供给曲线有什么联系 什么是需求收入弹性与需求的交叉价格弹性 1 Ascenario 一个故事 Youdesignwebsitesforlocalbusinesses Youcharge 200perwebsite andcurrentlysell12websitespermonth Yourcostsarerising includingtheopportunitycostofyourtime soyouconsiderraisingthepriceto 250 Thelawofdemandsaysthatyouwon tsellasmanywebsitesifyouraiseyourprice Howmanyfewerwebsites Howmuchwillyourrevenuefall ormightitincrease 你的工作是为本地企业制作网站 制作一个网站收费200美元 目前你每个月能卖出12个网站你的成本在不断上升 包括你的时间的机会成本 因此你考虑把价格升到250美元需求定理告诉我们 如果提高价格 你将不能卖出原来这么多的网站 你将少卖出多少网站 你的收益将会减少还是增加 减少或增加多少 0 2 ELASTICITYANDITSAPPLICATION 3 Elasticity弹性 Basicidea Elasticitymeasureshowmuchonevariablerespondstochangesinanothervariable Onetypeofelasticitymeasureshowmuchdemandforyourwebsiteswillfallifyouraiseyourprice Definition ElasticityisanumericalmeasureoftheresponsivenessofQdorQstooneofitsdeterminants 基本想法 弹性衡量一种变量对另一种变量反应程度的指标一种弹性衡量如果你提高价格 对你网站的需求会下降多少 定义 弹性衡量需求量或供给量对其某种决定因素的反应程度的指标 0 ELASTICITYANDITSAPPLICATION 4 PriceElasticityofDemand需求价格弹性 PriceelasticityofdemandmeasureshowmuchQdrespondstoachangeinP 需求价格弹性衡量一种物品需求量对其价格变动反应程度的指标 Looselyspeaking itmeasurestheprice sensitivityofbuyers demand 简单的说 它衡量卖者需求的价格敏感程度 0 ELASTICITYANDITSAPPLICATION 5 PriceElasticityofDemand Priceelasticityofdemandequals 0 Prisesby10 Qfallsby15 Example ELASTICITYANDITSAPPLICATION 6 PriceElasticityofDemand AlongaDcurve PandQmoveinoppositedirections whichwouldmakepriceelasticitynegative Wewilldroptheminussignandreportallpriceelasticitiesaspositivenumbers 需求与价格沿着需求曲线往相反方向变化 这使需求价格弹性为负 我们去掉负号 把所有价格弹性表示为正数 0 ELASTICITYANDITSAPPLICATION 7 CalculatingPercentageChanges 0 Demandforyourwebsites Standardmethodofcomputingthepercentage change GoingfromAtoB the changeinPequals 250 200 200 25 ELASTICITYANDITSAPPLICATION 8 CalculatingPercentageChanges 0 Demandforyourwebsites Thestandardmethodgivesdifferentanswersdependingonwhereyoustart 如果你的初始值不同 标准方法计算出来的结果也就不同 FromAtoB Prises25 Qfalls33 elasticity 33 25 1 33FromBtoA Pfalls20 Qrises50 elasticity 50 20 2 50 ELASTICITYANDITSAPPLICATION 9 CalculatingPercentageChanges So weinsteadusethemidpointmethod 0 Themidpointisthenumberhalfwaybetweenthestart endvalues theaverageofthosevalues 中点是初始值与终值的平均值Itdoesn tmatterwhichvalueyouuseasthe start andwhichasthe end yougetthesameanswereitherway 哪一点看作初始值还是终值并不重要 你都会得到相同的结果 ELASTICITYANDITSAPPLICATION 10 CalculatingPercentageChanges Usingthemidpointmethod the changeinPequals 0 The changeinQequals Thepriceelasticityofdemandequals ACTIVELEARNING1Calculateanelasticity 11 Usethefollowinginformationtocalculatethepriceelasticityofdemandforhotelrooms ifP 70 Qd 5000ifP 90 Qd 3000 ACTIVELEARNING1Answers 12 Usemidpointmethodtocalculate changeinQd 5000 3000 4000 50 changeinP 90 70 80 25 Thepriceelasticityofdemandequals ELASTICITYANDITSAPPLICATION 13 Whatdeterminespriceelasticity Tolearnthedeterminantsofpriceelasticity welookataseriesofexamples Eachcomparestwocommongoods Ineachexample Supposethepricesofbothgoodsriseby20 ThegoodforwhichQdfallsthemost inpercent hasthehighestpriceelasticityofdemand Whichgoodisit Why Whatlessondoestheexampleteachusaboutthedeterminantsofthepriceelasticityofdemand 为了找到需求价格弹性的决定因素 我们看下面的这些例子 每个例子都比较了两种物品 在每个例子中 假设两种物品的价格都上升了20 需求数量下降最大 百分比 的物品有最大的需求价格弹性 它是哪种物品 为什么 这个例子告诉我们什么是决定需求价格弹性的因素 0 ELASTICITYANDITSAPPLICATION 14 EXAMPLE1 Breakfastcerealvs Sunscreen谷类早餐vs 防晒霜 Thepricesofbothofthesegoodsriseby20 ForwhichgooddoesQddropthemost Why Breakfastcerealhasclosesubstitutes e g pancakes Eggowaffles leftoverpizza sobuyerscaneasilyswitchifthepricerises Sunscreenhasnoclosesubstitutes soconsumerswouldprobablynotbuymuchlessifitspricerises Lesson Priceelasticityishigherwhenclosesubstitutesareavailable 这两种物品的价格都上升20 哪种物品的需求数量下降的最多 为什么 谷类早餐有很多相近的替代品 比如 煎饼 Eggo华夫饼 剩余的皮萨等 如果价格上升买者可以很容易购买其他物品防晒霜没有类似的替代品 如果价格上升 消费者不可能少买太多总结 有相近替代品的物品的需求往往较富有弹性 0 ELASTICITYANDITSAPPLICATION 15 EXAMPLE2 BlueJeans vs Clothing 蓝色牛仔裤 与 衣服 Thepricesofbothgoodsriseby20 ForwhichgooddoesQddropthemost Why Foranarrowlydefinedgoodsuchasbluejeans therearemanysubstitutes khakis shorts Speedos Therearefewersubstitutesavailableforbroadlydefinedgoods Therearen ttoomanysubstitutesforclothing otherthanlivinginanudistcolony Lesson Priceelasticityishigherfornarrowlydefinedgoodsthanbroadlydefinedones 如果两种物品的价格都上涨20 哪种物品的需求量下降的最多 为什么 定义范围狭窄的物品比如蓝色牛仔裤有很多的替代品 卡其 短裤 Speedos等 定义范围宽泛的物品很少有替代品 衣服没有什么替代品 除非是流行裸体的殖民地 总结 范围小的市场的需求弹性往往大于范围大的市场的需求弹性 0 ELASTICITYANDITSAPPLICATION 16 EXAMPLE3 Insulinvs CaribbeanCruises胰岛素与加勒比游轮 Thepricesofbothofthesegoodsriseby20 ForwhichgooddoesQddropthemost Why Tomillionsofdiabetics insulinisanecessity Ariseinitspricewouldcauselittleornodecreaseindemand Acruiseisaluxury Ifthepricerises somepeoplewillforegoit Lesson Priceelasticityishigherforluxuriesthanfornecessities 如果两种物品的价格都上涨20 哪种物品的需求量下降的最多 为什么 对数以百万计的糖尿病患者来说 胰岛素是必需品 胰岛素价格的上升基本上不会引起需求的下降游轮是奢侈品 如果价格上升 有些人会放弃购买总结 奢侈品的需求弹性要大于必需品的需求弹性 0 ELASTICITYANDITSAPPLICATION 17 EXAMPLE4 GasolineintheShortRunvs GasolineintheLongRun短期的汽油与长期的汽油 Thepriceofgasolinerises20 DoesQddropmoreintheshortrunorthelongrun Why There snotmuchpeoplecandointheshortrun otherthanridethebusorcarpool Inthelongrun peoplecanbuysmallercarsorliveclosertowheretheywork Lesson Priceelasticityishigherinthelongrunthantheshortrun 汽油价格上涨20 短期还是长期的汽油需求量会下降更多 为什么 短期内 人们除了坐公交或者自己开车之外 并没有什么其他办法长期中 人们可以购买省油的小排量汽车或搬到上班地方附近居住总结 相对于短期 物品的需求往往在长期更富有弹性 0 ELASTICITYANDITSAPPLICATION 18 TheDeterminantsofPriceElasticity ASummary Thepriceelasticityofdemanddependson theextenttowhichclosesubstitutesareavailablewhetherthegoodisanecessityoraluxuryhowbroadlyornarrowlythegoodisdefinedthetimehorizon elasticityishigherinthelongrunthantheshortrun 需求价格弹性取决于 相近替代品的可获得性物品是必需品还是奢侈品物品的定义是宽泛还是狭义时间框架 长期比短期更富有弹性 0 ELASTICITYANDITSAPPLICATION 19 TheVarietyofDemandCurves各种需求曲线 Thepriceelasticityofdemandiscloselyrelatedtotheslopeofthedemandcurve Ruleofthumb Theflatterthecurve thebiggertheelasticity Thesteeperthecurve thesmallertheelasticity FivedifferentclassificationsofDcurves 需求价格弹性与需求曲线的斜率密切相关拇指规则 通过某一点的需求曲线越平坦 需求的价格弹性就越大通过某一点的需求曲线越陡峭 需求的价格弹性就越小需求曲线的五种不同分类 0 ELASTICITYANDITSAPPLICATION 20 Perfectlyinelasticdemand oneextremecase 完全无弹性的需求 一个极端例子 Pfallsby10 Qchangesby0 0 0 10 0 Consumers pricesensitivity 消费者的价格敏感度 Dcurve Elasticity vertical none 0 ELASTICITYANDITSAPPLICATION 21 Inelasticdemand 缺乏弹性的需求 Qriseslessthan10 0 10 10 1 Pfallsby10 Consumers pricesensitivity Dcurve Elasticity relativelysteep相对陡峭 relativelylow 1 ELASTICITYANDITSAPPLICATION 22 Unitelasticdemand 单位弹性需求 Qrisesby10 0 10 10 1 Pfallsby10 Consumers pricesensitivity Elasticity intermediate 1 Dcurve intermediateslope ELASTICITYANDITSAPPLICATION 23 Elasticdemand 富有弹性的需求 Qrisesmorethan10 0 10 10 1 Pfallsby10 Consumers pricesensitivity Dcurve Elasticity relativelyflat relativelyhigh 1 ELASTICITYANDITSAPPLICATION 24 Perfectlyelasticdemand theotherextreme 完全有弹性的需求 另一个极端例子 P1 Pchangesby0 Qchangesbyany 0 any 0 infinity无穷大 P2 Consumers pricesensitivity Dcurve Elasticity infinity horizontal extreme ELASTICITYANDITSAPPLICATION 25 ElasticityofaLinearDemandCurve线性需求曲线的弹性 0 Theslopeofalineardemandcurveisconstant butitselasticityisnot 线性需求曲线的斜率为常数 但它的弹性不是常数 ELASTICITYANDITSAPPLICATION 26 PriceElasticityandTotalRevenue总收益与需求价格弹性 Continuingourscenario ifyouraiseyourpricefrom 200to 250 wouldyourrevenueriseorfall Revenue PxQApriceincreasehastwoeffectsonrevenue HigherPmeansmorerevenueoneachunityousell Butyousellfewerunits lowerQ duetoLawofDemand Whichofthesetwoeffectsisbigger Itdependsonthepriceelasticityofdemand 继续我们的故事 如果你把价格从 200上升到 250 你的收益会增加还是减少 收益 PxQ价格上升对收益有两种影响 更高的价格意味着你在售出的每单位物品上会有更多的收益但根据需求定理 你售出的物品数量会减少两种影响哪种更大 这要取决于需求价格弹性 0 ELASTICITYANDITSAPPLICATION 27 PriceElasticityandTotalRevenue Ifdemandiselastic thenpriceelast ofdemand 1如果需求是有弹性的 那需求价格弹性 1 changeinQ changeinP需求量变动百分比 价格变动百分比ThefallinrevenuefromlowerQisgreaterthantheincreaseinrevenuefromhigherP sorevenuefalls 需求量减少使收益减少的幅度大于价格上升使收益增加的幅度 总收益减少 Revenue PxQ 0 ELASTICITYANDITSAPPLICATION 28 PriceElasticityandTotalRevenue Elasticdemand elasticity 1 8 WhenDiselastic apriceincreasecausesrevenuetofall 0 lostrevenueduetolowerQ increasedrevenueduetohigherP Demandforyourwebsites ELASTICITYANDITSAPPLICATION 29 PriceElasticityandTotalRevenue Ifdemandisinelastic thenpriceelast ofdemand 1 changeinQ changeinPThefallinrevenuefromlowerQissmallerthantheincreaseinrevenuefromhigherP sorevenuerises 需求量减少使收益减少的幅度小于价格上升使收益增加的幅度 总收益增加Inourexample supposethatQonlyfallsto10 insteadof8 whenyouraiseyourpriceto 250 Revenue PxQ 0 ELASTICITYANDITSAPPLICATION 30 PriceElasticityandTotalRevenue Now demandisinelastic elasticity 0 82 WhenDisinelastic apriceincreasecausesrevenuetorise 0 lostrevenueduetolowerQ increasedrevenueduetohigherP Demandforyourwebsites ACTIVELEARNING2Elasticityandexpenditure revenue弹性与支出 收益 A Pharmaciesraisethepriceofinsulinby10 Doestotalexpenditureoninsulinriseorfall B Asaresultofafarewar thepriceofaluxurycruisefalls20 Doesluxurycruisecompanies totalrevenueriseorfall A 药店将胰岛素的价格提高10 对胰岛素的总支出会增加还是减少 B 作为价格战的结果 游轮价格下降了20 游轮制造公司的收益会增加还是下降 31 ACTIVELEARNING2Answers 32 Pharmaciesraisethepriceofinsulinby10 Doestotalexpenditureoninsulinriseorfall 药店将胰岛素的价格提高10 对胰岛素的总支出会增加还是减少 Expenditure PxQSincedemandisinelastic Qwillfalllessthan10 soexpenditurerises 胰岛素的需求缺乏弹性 需求量下降幅度不超过10 因此支出增加 ACTIVELEARNING2Answers 33 B Asaresultofafarewar thepriceofaluxurycruisefalls20 Doesluxurycruisecompanies totalrevenueriseorfall 作为价格战的结果 游轮价格下降了20 游轮制造公司的收益会增加还是下降 Revenue PxQThefallinPreducesrevenue butQincreases whichincreasesrevenue Whicheffectisbigger Sincedemandiselastic Qwillincreasemorethan20 sorevenuerises ELASTICITYANDITSAPPLICATION 34 APPLICATION DoesDrugInterdictionIncreaseorDecreaseDrug RelatedCrime 禁毒增加还是减少了与毒品相关的犯罪 Onesideeffectofillegaldruguseiscrime Usersoftenturntocrimetofinancetheirhabit Weexaminetwopoliciesdesignedtoreduceillegaldruguseandseewhateffectstheyhaveondrug relatedcrime Forsimplicity weassumethetotaldollarvalueofdrug relatedcrimeequalstotalexpenditureondrugs Demandforillegaldrugsisinelastic duetoaddictionissues 使用毒品的一个不利影响是犯罪 吸毒上瘾的人往往会有暴力犯罪 以得到吸毒所需要的钱我们比较两种旨在减少吸毒的政策 并观察它们对与毒品相关的犯罪的影响为简化起见 我们假定与毒品相关的犯罪的美元价值等于购买毒品的总支出由于吸毒成瘾 非法毒品的需求是缺乏弹性的 0 ELASTICITYANDITSAPPLICATION 35 Policy1 Interdiction禁毒 0 Interdictionreducesthesupplyofdrugs Sincedemandfordrugsisinelastic Prisespropor tionallymorethanQfalls Result anincreaseintotalspendingondrugs andindrug relatedcrime在毒品上的总支出和与毒品相关的犯罪都会增加 ELASTICITYANDITSAPPLICATION 36 Policy2 Education 0 Educationreducesthedemandfordrugs PandQfall Result Adecreaseintotalspendingondrugs andindrug relatedcrime 结果 在毒品上的总支出和与毒品相关的犯罪都减少 ELASTICITYANDITSAPPLICATION 37 PriceElasticityofSupply PriceelasticityofsupplymeasureshowmuchQsrespondstoachangeinP 供给价格弹性衡量一种物品供给量对其价格变动反应程度的指标 Looselyspeaking itmeasuressellers price sensitivity Again usethemidpointmethodtocomputethepercentagechanges 继续使用中点法计算变动的百分比 0 ELASTICITYANDITSAPPLICATION 38 PriceElasticityofSupply Priceelasticityofsupplyequals 0 Prisesby8 Qrisesby16 Example ELASTICITYANDITSAPPLICATION 39 TheVarietyofSupplyCurves Theslopeofthesupplycurveiscloselyrelatedtopriceelasticityofsupply Ruleofthumb Theflatterthecurve thebiggertheelasticity Thesteeperthecurve thesmallertheelasticity Fivedifferentclassifications 供给价格弹性与供给曲线的斜率密切相关拇指规则 通过某一点的供给曲线越平坦 供给的价格弹性就越大通过某一点的供给曲线越陡峭 供给的价格弹性就越小五种不同的分类 0 ELASTICITYANDITSAPPLICATION 40 Perfectlyinelastic oneextreme Q1 P1 Qchangesby0 0 0 10 0 Prisesby10 Sellers pricesensitivity Scurve Elasticity vertical none 0 ELASTICITYANDITSAPPLICATION 41 Inelastic Q1 P1 Qriseslessthan10 0 10 10 1 Prisesby10 Sellers pricesensitivity Scurve Elasticity relativelysteep relativelylow 1 ELASTICITYANDITSAPPLICATION 42 Unitelastic Q1 P1 Qrisesby10 0 10 10 1 Prisesby10 Sellers pricesensitivity Scurve Elasticity intermediateslope intermediate 1 ELASTICITYANDITSAPPLICATION 43 Elastic Q1 P1 Qrisesmorethan10 0 10 10 1 Prisesby10 Sellers pricesensitivity Scurve Elasticity relativelyflat relativelyhigh 1 ELASTICITYANDITSAPPLICATION 44 Perfectlyelastic theotherextreme P1 Pchangesby0 Qchangesbyany 0 any 0 infinity P2 Sellers pricesensitivity Scurve Elasticity horizontal extreme infinity ELASTICITYANDITSAPPLICATION 45 TheDeterminantsofSupplyElasticity Themoreeasilysellerscanchangethequantitytheyproduce thegreaterthepriceelasticityofsupply Example Supplyofbeachfrontpropertyishardertovaryandthuslesselasticthansupplyofnewcars Formanygoods priceelasticityofsupplyisgreaterinthelongrunthanintheshortrun becausefirmscanbuildnewfactories ornewfirmsmaybeabletoenterthemarket 卖者越容易改变他们的生产数量 供给价格弹性越大例如 海滨别墅的供给较难改变 因此其供给弹性要低于新汽车的供给弹性对许多物品而言 长期供给价格弹性都要大于短期供给价格弹性 这是因为企业在长期能建更多的工厂 或者新的企业能够进入市场 ACTIVELEARNING3Elasticityandchangesinequilibrium 46 Thesupplyofbeachfrontpropertyisinelastic Thesupplyofnewcarsiselastic 海滨别墅的供给缺乏弹性的 而新汽车的供给是富有弹性的Supposepopulationgrowthcausesdemandforbothgoodstodouble ateachprice Qddoubles 假设人口数量的增长使对两种物品的需求都翻了一番 就是在在每种价格水平上 需求量加倍 ForwhichproductwillPchangethemost 哪种物品的价格变动更大 ForwhichproductwillQchangethemost 哪种物品的产量变动更大 ACTIVELEARNING3Answers 47 Beachfrontproperty海滨别墅 inelasticsupply Whensupplyisinelastic anincreaseindemandhasabiggerimpactonpricethanonquantity 供给缺乏弹性时 需求增加使价格上升的比例要大于产量增加的比例 ACTIVELEARNING3Answers 48 Newcars elasticsupply Whensupplyiselastic anincreaseindemandhasabiggerimpactonquantitythanonprice 供给富有弹性时 需求增加使产量增加的比例要大于价格上升的比例 ELASTICITYANDITSAPPLICATION 49 HowthePriceElasticityofSupplyCanVary供给价格弹性会如何变动 0 SupplyoftenbecomeslesselasticasQrises duetocapacitylimits 由于生产能力限制 当供给量越大时 供给价格弹性越小 elasticity 1 elasticity 1 ELASTICITYANDITSAPPLICATION 50 OtherElasticities Incomeelasticityofdemand measurestheresponseofQdtoachangeinconsumerincome需求收入弹性 衡量消费者收入变动时需求量如何变动 RecallfromChapter4 Anincreaseinincomecausesanincreaseindemandforanormalgood Hence fornormalgoods incomeelasticity 0 Forinferiorgoods incomeelasticity 0 ELASTICITYANDITSAPPLICATION 51 OtherElasticities Cross priceelasticityofdemand measurestheresponseofdemandforonegoodtochangesinthepriceofanothergood需求的交叉价格弹性 衡量一种物品需求量对另外一种物品价格变动的反应程度 Forsubstitutes cross priceelasticity 0 e g anincreaseinpriceofbeefcausesanincreaseindemandforchicken Forcomplements cross priceelasticity 0 e g anincreaseinpriceofcomputerscausesdecreaseindemandforsoftware ELASTICITYANDITSAPPLICATION 52 Cross PriceElasticitiesintheNews AsGasCostsSoar BuyersFlocktoSmallCars NewYorkTimes 5 2 2008 GasPricesDriveStudentstoOnlineCourses ChronicleofHigherEducation 7 8 2008 Gaspric