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    今日福彩3d好运彩字谜 0405弹性及其应用

    3d藏机图:0405弹性及其应用.ppt

    0405弹性及其应用

    ranfand
    2019-03-07 0人阅读 举报 0 0 0 暂无简介

    今日福彩3d好运彩字谜 www.qwbcf.com 简介:本文档为《0405弹性及其应用ppt》,可适用于市场营销领域

    经济学原理陈志广南京大学政府管理学院chenzhiguangnjueducn第四讲弹性及其应用一、需求弹性二、供给弹性三、应用弹性基本想法: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*Here,QdandQsareshortforquantitydemandedandquantitysupplied,asinthePowerPointforChapter需求价格弹性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简单的说它衡量卖者需求的价格敏感程度需求价格弹性需求价格弹性等于P上升Q下降例如:需求价格弹性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*ItmightbeworthexplainingtoyourstudentsthatldquoPandQmoveinoppositedirectionsrdquomeansthatthepercentagechangeinQandthepercentagechangeinPwillhaveoppositesigns,thusimplyinganegativepriceelasticityTobeconsistentwiththetext,thelaststatementinthegreenboxsaysthatwewillreportallpriceelasticitiesaspositivenumbersItmightbeslightlymoreaccuratetosaythatwewillreportallelasticitiesasnonnegativenumbers:wewanttoallowforthe(admittedlyrare)caseofzeroelasticity计算变动百分比对你网站的需求计算百分比()变化的标准方法:从A到B价格变化百分比等于:($ndash$)$=计算变动百分比对你网站的需求问题:如果你的初始值不同标准方法计算出来的结果也就不同从A到B,P上升,Q下降,弹性==从B到A,P下降,Q上升,弹性==计算变动百分比因此我们采用中点法计算弹性:中点是初始值与终值的平均值哪一点看作初始值还是终值并不重要你都会得到相同的结果计算弹性*利用下述数据计算宾馆房间的需求价格弹性:如果P=$Qd=如果P=$Qd=计算弹性*采用中点法计算需求数量的变动百分比:(ndash)=价格的变动百分比:($ndash$)$=需求的价格弹性等于:采用中点法价格的变动百分比等于数量的变动百分比等于:需求的价格弹性等于:*Thesecalculationsarebasedontheexampleshownafewslidesback:pointsAandBonthewebsitedemandcurve价格弹性由什么决定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*Inessence,thetextbooksaysldquoHerearethedeterminantsofelasticityThefirstoneisavailabilityofclosesubstitutesHerersquosanexamplehelliprdquoThatrsquosgreatforatextbookForteaching,Irsquovefoundadifferentapproachtobefarmoreeffective:havingstudentsdeducethegenerallessonsfromspecificexamplestheycanfigureoutusingcommonsenseThisistheapproachonthenextfewslidesAlso,seenotesonthenextslideforagoodsuggestion例:谷类早餐与防晒霜这两种物品的价格都上升。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*Suggestion:Foreachoftheseexamples,displaytheslidetitle(whichliststhetwogoods)andthefirsttwolinesoftext(whichaskwhichgoodexperiencesthebiggestdropindemandinresponsetoapriceincrease)GiveyourstudentsaquietminutetoformulatetheiranswersThen,askforvolunteers例:ldquo蓝色牛仔裤rdquo与ldquo衣服rdquo如果两种物品的价格都上涨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*YoumightneedtoclarifythenatureofthisthoughtexperimentHere,welookattwoalternatescenariosInthefirst,thepriceofbluejeans(andnootherclothing)risesby,andweobservethepercentagedecreaseinquantityofbluejeansdemandedInthesecondscenario,thepriceofallclothingrisesby,andweobservethepercentagedecreaseindemandforallclothing例:胰岛素与加勒比游轮如果两种物品的价格都上涨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例:短期的汽油与长期的汽油汽油价格上涨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决定需求价格弹性的因素:一个总结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mdash长期比短期更富有弹性*Thisslideisaconvenienceforyourstudents,andreplicatesasimilartablefromthetextIfyoursquorepressedfortime,itisprobablysafetoomitthisslidefromyourpresentation各种需求曲线需求价格弹性与需求曲线的斜率密切相关拇指规则(经验规则:ruleofthumb):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hellip*EconomistsclassifydemandcurvesaccordingtotheirelasticityThenextslidespresentthefivedifferentclassifications,fromleasttomostelasticldquo完全无弹性的需求rdquo(一个极端例子)价格下降需求量变动=消费者的价格敏感度:需求曲线弹性:垂直不敏感*IfQdoesnrsquotchange,thenthepercentagechangeinQequalszero,andthuselasticityequalszeroItishardtothinkofagoodforwhichthepriceelasticityofdemandisliterallyzeroTakeinsulin,forexampleAsufficientlylargepriceincreasewouldprobablyreducedemandforinsulinalittle,particularlyamongpeoplewithverylowincomesandnohealthinsuranceHowever,ifelasticityisveryclosetozero,thenthedemandcurveisalmostverticalInsuchcases,theconvenienceofmodelingdemandasperfectlyinelasticprobablyoutweighsthecostofbeingslightlyinaccurateldquo缺乏弹性的需求rdquo需求量上升价格下降消费者的价格敏感度:需求曲线:弹性相对陡峭相对小*Anexample:StudentdemandfortextbooksthattheirprofessorshaverequiredfortheircoursesHere,itrsquosalittlemoreclearthatelasticitywouldbesmall,butnotzeroAtahighenoughprice,somestudentswillnotbuytheirbooks,butinsteadwillsharewithafriend,ortrytofindtheminthelibrary,orjusttakecopiousnotesinclassAnotherexample:Gasolineintheshortrunldquo单位弹性需求rdquo需求量上升=价格下降消费者的价格敏感度:弹性:中等需求曲线:中等斜率*Thisistheintermediatecase:thedemandcurveisneitherrelativelysteepnorrelativelyflatBuyersareneitherrelativelypricesensitivenorrelativelyinsensitivetoprice(Thisisalsothecasewherepricechangeshavenoeffectonrevenue)ldquo富有弹性的需求rdquo需求量增加超过价格下降消费者的价格敏感度:需求曲线:弹性:相对平坦相对敏感*Agoodexampleherewouldbebreakfastcereal,ornearlyanythingwithreadilyavailablesubstitutesAnelasticdemandcurveisflatterthanaunitelasticdemandcurve(whichitselfisflatterthananinelasticdemandcurve)ldquo完全有弹性的需求rdquoP价格变动需求量变动为任意任意=无穷大P=消费者的价格敏感度:需求曲线:弹性:无穷大水平非常敏感*ldquoExtremepricesensitivityrdquomeansthetiniestpriceincreasecausesdemandtofalltozeroldquoQchangesbyanyrdquondashwhentheDcurveishorizontal,quantitycannotbedeterminedfrompriceConsumersmightdemandQunitsonemonth,Qunitsanothermonth,andsomeotherquantitylaterQcanchangebyanyamount,butPalwaysldquochangesbyrdquo(ie,doesnrsquotchange)Ifperfectlyinelasticisoneextreme,thiscase(perfectlyelastic)istheotherHerersquosagoodrealworldexampleofaperfectlyelasticdemandcurve,whichforeshadowsanupcomingchapteronfirmsincompetitivemarketsSupposeyourunasmallfamilyfarminIowaYourmaincropiswheatThedemandcurveinthismarketisdownwardsloping,andthemarketdemandandsupplycurvesdeterminethepriceofwheatSupposethatpriceis$bushelNowconsiderthedemandcurvefacingyou,theindividualwheatfarmerIfyouchargeapriceof$,youcansellasmuchoraslittleasyouwantIfyouchargeapriceevenjustalittlehigherthan$,demandforYOURwheatwillfalltozero:Buyerswouldnotbewillingtopayyoumorethan$whentheycouldgetthesamewheatelsewherefor$Similarly,ifyoudropyourpricebelow$,thendemandforYOURwheatwillbecomeenormous(notliterallyinfinite,butldquoalmostinfiniterdquo):ifotherwheatfarmersarecharging$andyouchargeless,thenEVERYbuyerwillwanttobuywheatfromyouWhyisthedemandcurvefacinganindividualproducerperfectlyelasticRecallthatelasticityisgreaterwhenlotsofclosesubstitutesareavailableInthiscase,youaresellingaproductthathasmanyperfectsubstitutes:thewheatsoldbyeveryotherfarmerisaperfectsubstituteforthewheatyousell线性需求曲线的弹性线性需求曲线的斜率为常数但它的弹性不是常数*ThematerialonthisslideisnotusedanywhereelseinthetextbookTherefore,ifyouarepressedfortimeandlookingforthingstocut,youmightconsidercuttingthisslide(NotethatthisismypersonalrecommendationandisnotnecessarilytheofficialpositionofGregMankiworCengageSouthWestern)Duetospacelimitations,thisslideusesldquoErdquoasanabbreviationforelasticity,ormorespecifically,thepriceelasticityofdemand,andtheslideomitstheanalysisofrevenuealongthedemandcurveCalculationsofpercentagechangesusethemidpointmethod(ThisiswhytheincreasefromQ=toQ=isratherthaninfinity)Asyoumovedownalineardemandcurve,theslope(theratiooftheabsolutechangeinPtothatinQ)remainsconstant:Fromthepoint(,$)tothepoint(,$),theldquoriserdquoequals$,theldquorunrdquoequals,sotheslopeequalsorFromthepoint(,$)tothepoint(,$),theldquoriserdquoagainequals$,theldquorunrdquoequals,andtheslopeagainequalsHowever,thepercentagechangesinthesevariablesdonotremainconstant,asshownbythedifferentcoloredelasticitycalculationsthatappearontheslideThelessonhereisthatelasticityfallsasyoumovedownwardrightwardalongalineardemandcurve总收益与需求价格弹性继续我们的故事如果你把价格从$上升到$你的收益会增加还是减少?收益=PxQ价格上升对收益有两种影响:更高的价格意味着你在售出的每单位物品上会有更多的收益但根据需求定理你售出的物品数量会减少两种影响哪种更大?这要取决于需求价格弹性*WereturntoourscenarioItrsquosnothardforstudentstoimaginebeinginthispositionndashrunningtheirownbusinessandtryingtodecidewhethertoraisethepriceTomostofyourstudents,itshouldbeclearthatmakingthebestpossibledecisionwouldrequireinformationaboutthelikelyeffectsofthepriceincreaseonrevenueThatiswhyelasticityissohelpful,aswewillnowseehellip总收益与需求价格弹性如果需求是有弹性的那需求价格弹性需求量变动百分比价格变动百分比需求量减少使收益减少的幅度大于价格上升使收益增加的幅度总收益减少收益=PxQ总收益与需求价格弹性富有弹性的需求(弹性=)当需求富有弹性时价格上升会使收益减少需求量减少所损失的收益价格上升所增加的收益*IntheldquoNormalrdquoview(editmode),thelabelsoverthegraphlookcluttered,liketheyrsquoreontopofeachotherThisisnotamistakendashinldquoSlideShowrdquomode(presentationmode),allwillbefinendashtryit!Pointouttostudentsthatthearea(outlinedinblue)representinglostrevenueduetolowerQislargerthanthearea(outlinedinyellow)representingincreasedrevenueduetohigherPHence,theneteffectisafallinrevenue总收益与需求价格弹性如果需求是缺乏弹性的那需求价格弹性需求量变动的百分比价格变动的百分比需求量减少使收益减少的幅度小于价格上升使收益增加的幅度总收益增加在我们下面的例子中当你提高价格到$时假定需求量只减少到(而不是)收益=PxQ总收益与需求价格弹性现在需求是缺乏弹性的:弹性=当需求缺乏弹性时价格上升会使收益增加需求量减少所损失的收益价格上升所增加的收益*Again,theslideappearsclutteredinldquoNormalrdquoview(editmode),buteverythingisfinewhendisplayedinldquoSlideShowrdquomode(presentationmode)PointouttostudentsthatthearearepresentinglostrevenueduetolowerQissmallerthanthearearepresentingincreasedrevenueduetohigherPHence,theneteffectisanincreaseinrevenueTheknifeedgecase,notshownherebutperhapsworthmentioninginclass,isunitelasticdemandInthatcase,anincreaseinpriceleavesrevenueunchanged:theincreaseinrevenuefromhigherPexactlyoffsetsthelostrevenueduetolowerQ弹性与支出收益A药店将胰岛素的价格提高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。游轮制造公司的收益会增加还是下降?*Theseproblems,perhapssimilartothoseyoumightaskonanexam,arecomplexinthattheytestseveralskillsatonce:studentsmustdeterminewhetherdemandforeachgoodiselasticorinelastic,andtheymustdeterminetheimpactofapricechangeonrevenueexpenditureSofar,wersquovebeentalkingabouthowelasticitydeterminestheeffectsofanincreaseinPonrevenuePart(b)asksyourstudentstodeterminetheeffectsofadecreaseinP*A药店将胰岛素的价格提高对胰岛素的总支出会增加还是减少?支出=PxQ胰岛素的需求缺乏弹性需求量下降幅度不超过因此支出增加*B作为价格战的结果游轮价格下降了。游轮制造公司的收益会增加还是下降?收益=PxQ价格下降减少了收益但销售量增多会增加收益。哪个影响更大?由于需求富有弹性销售量增加比例会超过因此收益增加Thefirstpartoftheexplanationdiscussestheopposingeffectsonrevenueitspurposeistoclarifytheeffectsofapricedecreaseonrevenue,aswehavepreviouslyonlydiscussedtheeffectsofapriceincrease供给价格弹性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简单的说它测量了卖者了价格敏感度继续使用中点法计算变动的百分比*MosteverythingintheldquopriceelasticityofsupplyrdquosectioncorrespondstoanalogousconceptsfromtheldquopriceelasticityofdemandrdquosectionSo,itisprobablysafetomovethroughthissectionmorequickly供给价格弹性供给价格弹性为:价格上升需求量增加例:各种供给曲线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hellip*EconomistsclassifysupplycurvesaccordingtotheirelasticityThenextslidespresentthedifferentclassifications,fromleasttomostelasticldquo完全无弹性的供给rdquo(一个极端)QP供给量变动=价格上升卖者的价格敏感度:供给曲线:弹性:垂直不敏感ldquo缺乏弹性的供给rdquoQP供给量增加比例小于价格上升卖者的价格敏感度:供给曲线:弹性:相对陡峭相对小ldquo单位弹性供给rdquoQP供给量增加=价格上升卖者的价格敏感度:供给曲线:弹性:中等斜率中等=ldquo富有弹性的供给rdquoQP供给量增加大于价格上升卖者的价格敏感度:供给曲线:弹性:相对平坦相对敏感ldquo完全有弹性的供给rdquo(另一个极端)P价格不变供给量变动任意百分比任意=无穷大P=卖者的价格敏感度:供给曲线:弹性:水平很敏感无穷大供给价格弹性的决定因素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*Thissectionisnotperfectlyanalogoustothesectiononthedeterminantsofthepriceelasticityofdemand,butitrsquossimilarenoughthatyoucanprobablycoveritmorequicklyandwithmuchlesshandholding弹性与均衡的改变*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)哪种物品的价格变动更大?哪种物品的产量变动更大?ThisisoneoftheldquoProblemsandApplicationsrdquoattheendofthechapter*海滨别墅(供给缺乏弹性)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Inthisslideandthenext,theinitialpriceandquantityandthetwodemandcurvesarethesameTheonlydifferenceistheelasticityofsupplyandslopeofthesupplycurveTheDcurveshiftstotheright,butnotinaparallelfashion:ateachprice,quantitydemandedistwiceashigh,sothenewDcurvewillbeflatterthantheinitialoneInthetextboxcontainingtheverbalexplanation,ldquobiggerimpactrdquoisshorthandforldquobiggerpercentageimpactrdquoorldquobiggerproportionalimpactrdquo*新汽车(供给富有弹性)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供给价格弹性会如何变动由于生产能力限制当供给量越大时供给价格弹性越小弹性弹性*ThisgraphreplicatestheoneinFigureNote:ThegraphhereisnotquitedrawntoscaleWhenthepricerisesfrom$to$(aincrease,usingthemidpointmethod),quantityrisesfromto(or)Because,priceelasticityofsupplyisgreaterthanoneWhenthepricerisesfrom$to$(),quantityrisesfromto(about),sopriceelasticityofsupplyislessthanoneThewayIliketoexplainthisisasfollows:Whenoutputisverylow,itisrelativelyeasyforfirmstoincreaseoutputTheymayhaveexcesscapacity,ortheyarenotrequiringfulleffortfromtheirworkersIncreasingoutputisnotdifficult,soitdoesnrsquottakemuchofanincreaseinpricetoinduceanincreaseinproductionWhenoutputisveryhigh,itisrelativelyexpensiveforfirmstoincreaseoutpurther:therersquoslittleornoexcesscapacity,theyarealreadyrunningtheirfactoriesandmachinesatahighlevelofintensityToincreaseoutpurther,theymighthavetopaytheirworkersovertime,andtheirmachinesexperiencemorewearandtearandthereforerequiremorerepairsSo,athighlevelsofoutput,ittakesamuchlargerpriceincreasetomakefirmswillingtoincreaseoutpurtherEventually,firmsbumpupagainsttheircapacityconstraints,andsimplycannotincreaseoutputinresponsetofurtherpriceincreasesOfcourse,allofthisappliestotheshortrunInthelongrun,firmscanbuildmorefactories,and(dependingonthemarketstructure)newfirmscanenterthemarketRealworldexample:Inthepeaksummerdrivingseason,gasolinedemandishighestManyrefineriesareproducingnearcapacity,sothesupplycurveissteepInothermonths,whendemandislower,refinerieshavemoreexcesscapacity,andthesupplycurveisnotassteep其他弹性需求收入弹性:衡量消费者收入变动时需求量如何变动对正常物品而已收入增加时需求量增加也会增加因此正常物品的需求收入弹性低档物品的需求收入弹性*Thistopicandthenextone(crosspriceelasticity)donotappearanywhereelseinthebookInstructorswhoarepressedfortimemayconsidercuttingthesetopics(Thisismerelymysuggestion,nottheofficialpositionofGregMankiworCengageSouthWestern)其他弹性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替代品的交叉价格弹性(例如牛肉价格上升使对鸡肉的需求增加)互补品的交叉价格弹性(例如计算机价格上升使对软件的需求减少)应用:禁毒增加还是减少了与毒品相关的犯罪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*Inthetextbook,thisapplicationappearsneartheendofthechapter,andyoucaneasilymovetheseslidestotheendifyouwishtoteachthingsinthesameorderasthebookHowever,IencourageyoutoconsiderteachingthisapplicationrighthereimmediatelyafterthesectiononpriceelasticityofdemandItissafetodoso,asthisapplicationonlyrequiresknowledgeofpriceelasticityofdemandAlso,puttingtheapplicationherebreaksupwhatwouldotherwisebeaverylongsectionoftheorywitharealworldexamplethatmoststudentsfindveryinterestingKnowingelasticityhelpsusunderstandwhatmightotherwisebeacounterintuitiveresult(thatdruginterdictionincreasesdrugrelatedcrimeratherthanreducingit)政策:禁毒禁毒减少了毒品供给由于毒品的需求是缺乏弹性的毒品价格提高的比例会大于毒品使用减少的比例结果:在毒品上的总支出和与毒品相关的犯罪都会增加*Bythetimeallelementshaveappearedonthescreen,theslidewilllookkindofbusyIthinkthisisokay,becausetheelementsappearonthescreenonebyone,sostudentshavetimetoabsorbeachonebeforethenextoneappearsHowever,ifyoursquodratherstriptheslidedownabit,herersquosasuggestion:inldquoNormalrdquoview(whichoneusestoeditslides),youcandeletetheboxesthatrepresenttheinitialandnewvaluesofdrugrelatedcrime,andtheaccompanyingcaptionsThen,whenpresentingthisslideinclass,simplypointout(withyourmousecursor,alaserpointer,orevenyourarmsandhands)theareasthatrepresenttheinitialandnewvaluesofdrugrelatedcrime政策:教育教育减少对毒品的需求价格与需求量都下降结果:在毒品上的总支出和与毒品相关的犯罪都减少了禁毒、禁娼、禁酒等带来的意料之外效果吸引违法相对优势者暴力、犯罪生产提供更有价值产品密集产品缺乏信息与伪劣产品思考:不能忽视私人反应(连锁反应)哪种效应主导谁主导*Here,QdandQsareshortforquantitydemandedandquantitysupplied,asinthePowerPointforChapter*ItmightbeworthexplainingtoyourstudentsthatldquoPandQmoveinoppositedirectionsrdquomeansthatthepercentagechangeinQandthepercentagechangeinPwillhaveoppositesigns,thusimplyinganegativepriceelasticityTobeconsistentwiththetext,thelaststatementinthegreenboxsaysthatwewillreportallpriceelasticitiesaspositivenumbersItmightbeslightlymoreaccuratetosaythatwewillreportallelasticitiesasnonnegativenumbers:wewanttoallowforthe(admittedlyrare)caseofzeroelasticity*Thesecalculationsarebasedontheexampleshownafewslidesback:pointsAandBonthewebsitedemandcurve*Inessence,thetextbooksaysldquoHerearethedeterminantsofelasticityThefirstoneisavailabilityofclosesubstitutesHerersquosanexamplehelliprdquoThatrsquosgreatforatextbookForteaching,Irsquovefoundadifferentapproachtobefarmoreeffective:havingstudentsdeducethegenerallessonsfromspecificexamplestheycanfigureoutusingcommonsenseThisistheapproachonthenextfewslidesAlso,seenotesonthenextslideforagoodsuggestion*Suggestion:Foreachoftheseexamples,displaytheslidetitle(whichliststhetwogoods)andthefirsttwolinesoftext(whichaskwhichgoodexperiencesthebiggestdropindemandinresponsetoapriceincrease)GiveyourstudentsaquietminutetoformulatetheiranswersThen,askforvolunteers*YoumightneedtoclarifythenatureofthisthoughtexperimentHere,welookattwoalternatescenariosInthefirst,thepriceofbluejeans(andnootherclothing)risesby,andweobservethepercentagedecreaseinquantityofbluejeansdemandedInthesecondscenario,thepriceofallclothingrisesby,andweobservethepercentagedecreaseindemandforallclothing*Thisslideisaconvenienceforyourstudents,andreplicatesasimilartablefromthetextIfyoursquorepressedfortime,itisprobablysafetoomitthisslidefromyourpresentation*EconomistsclassifydemandcurvesaccordingtotheirelasticityThenextslidespresentthefivedifferentclassifications,fromleasttomostelastic*IfQdoesnrsquotchange,thenthepercentagechangeinQequalszero,andthuselasticityequalszeroItishardtothinkofagoodforwhichthepriceelasticityofdemandisliterallyzeroTakeinsulin,forexampleAsufficientlylargepriceincreasewouldprobablyreducedemandforinsulinalittle,particularlyamongpeoplewithverylowincomesandnohealthinsuranceHowever,ifelasticityisveryclosetozero,thenthedemandcurveisalmostverticalInsuchcases,theconvenienceofmodelingdemandasperfectlyinelasticprobablyoutweighsthecostofbeingslightlyinaccurate*Anexample:StudentdemandfortextbooksthattheirprofessorshaverequiredfortheircoursesHere,itrsquosalittlemoreclearthatelasticitywouldbesmall,butnotzeroAtahighenoughprice,somestudentswillnotbuytheirbooks,butinsteadwillsharewithafriend,ortrytofindtheminthelibrary,orjusttakecopiousnotesinclassAnotherexample:Gasolineintheshortrun*Thisistheintermediatecase:thedemandcurveisneitherrelativelysteepnorrelativelyflatBuyersareneitherrelativelypricesensitivenorrelativelyinsensitivetoprice(Thisisalsothecasewherepricechangeshavenoeffectonrevenue)*Agoodexampleherewouldbebreakfastcereal,ornearlyanythingwithreadilyavailablesubstitutesAnelasticdemandcurveisflatterthanaunitelasticdemandcurve(whichitselfisflatterthananinelasticdemandcurve)*ldquoExtremepricesensitivityrdquomeansthetiniestpriceincreasecausesdemandtofalltozeroldquoQchangesbyanyrdquondashwhentheDcurveishorizontal,quantitycannotbedeterminedfrompriceConsumersmightdemandQunitsonemonth,Qunitsanothermonth,andsomeotherquantitylaterQcanchangebyanyamount,butPalwaysldquochangesbyrdquo(ie,doesnrsquotchange)Ifperfectlyinelasticisoneextreme,thiscase(perfectlyelastic)istheotherHerersquosagoodrealworldexampleofaperfectlyelasticdemandcurve,whichforeshadowsanupcomingchapteronfirmsincompetitivemarketsSupposeyourunasmallfamilyfarminIowaYourmaincropiswheatThedemandcurveinthismarketisdownwardsloping,andthemarketdemandandsupplycurvesdeterminethepriceofwheatSupposethatpriceis$bushelNowconsiderthedemandcurvefacingyou,theindividu

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