第5章-需求和消费者行为

需求与消费者行第5淘宝西邦考 选择和效用理淘宝西邦考 消费者行Theconceptofindividualchoiceisoneofthemostimportantineconomics.Economicsrelaysonthefundamentalpremise(基本假定)thatpeopletendtochoosethosegoodsandservicestheyvaluemost淘宝西邦考 效用理Utilitydenotessatisfaction.Moreprecisely,itreferstohowconsumersrankdifferentgoodsandservices.Inthetheoryofdemand,wesaythat izetheirutility,whichmeansthattheychoosethebundleofconsumptiongoods消费品束thatmost淘宝西邦考 背景知识：边1870s前期，英国的杰文斯、侨居的法国人瓦尔拉和奥地利的门格尔，三人发起“边际”。WilliamS.Jevons

Léon

CarlMenger淘宝西邦考 边际效用价值掀起边际的学者用倡导并发扬“边际效用价值论”，用效用价值论与当时的劳动价值论相对抗，以边际分析方法取代当时的平均分析方法，因而成Marginalutilityistheadditionalutilityderivedfromaoneunitincreasein淘宝西邦考 总效用和边际效消费数 （总）效 边际效 淘宝西邦考 总效用和边际效用的关Q i Q边际效用递减定Marginal Marginal西邦考 效用理论的历DanielBernoulli伯努利amemberofabrilliantSwissfamilyofmathematicians,observedin1738thatpeopleactasifthedollartheystandtogaininafairbet赌)isworthlesstothemthanthedollartheystandtoThismeansthatsuccessive(连续的)newdollarsofwealthbringthemsmallerandsmallerincrements(增量)oftrueutility.淘宝西邦考 JeremyBentham

JeremyBentham(边沁)proposedthatsocietyshouldbeorganizedontheprincipleofutility‖whichhedefinedasthe―prpertyproducepleasure,goodorhappinessortoprevent…pain,evilorunhappiness.‖淘宝西邦考 功利主义的观Alllegislation( shouldbedesignedonutilitarianprinciples(功利原则)topromotetheeatesthappinessofthegreatestTheyevendevelopedameasureofpleasuretheycalledtheutil.淘宝西邦考 序数效Anordinal序数measuresimplyranksgoodsrelativetooneanother.Youcansayyoulikepeasbetterthanbroccoli花椰菜andyoulikeicecreambetterthanbothofthosevegetablesbutyoudon’treallyneedtosayhowmuchtorankyourpreferences(偏好)forthese淘宝西邦考 背景知淘宝西邦考 等边际原淘宝西邦考 消费者的最优Weassumethatconsumers utilitysubjecttoabudgetor Consumershaveacertainamountofetospendand,subjecttotheirbudgetconstraint预算约束andgivenofprices,theywillchooseabasketofgoodsthatwillprovidethemwiththegreatestutilityorsatisfaction.淘宝西邦考 问题：最优支出原淘宝西邦考 简化的例淘宝西邦考 衣服和食物123456789方案1：总效用8040120方案2：总效用≈10810118最优方案淘宝西邦考 效用最大的开1234567898642654321用于衣服，总效用=98+27=125。问题：如果有16元钱，应该怎样开淘宝西邦考 最优开支判别方金1234567898642654321淘宝西邦考 最后（边际）1元钱的效1i

×物i的边际效1元收入增加的即1元钱可以=1元钱 ×1单位商品 淘宝西邦考 收入最优花费的条件物品1的边际效用1=物品2的边际效用1 简写为以下资源配置最优的等边际物品1的边际效用=物品2的边际效用物品1的价格 物品2的价格

=淘宝西邦考 边际不等时的改善方物品1的边际效用

=物品物品移动1元，效用净增物品物品增加1增加1元支效用增加减少1元支效用减少淘宝西邦考 等边际原Utilityis izedwhenthemarginalutilityofthelastdollarspentoneachgoodisexactlythesameasthemarginalutilityofthelastdollarspentonanyothergood.Thisistheutility- izingruleortheequimarginalprinciple(效用最大化准则淘宝西邦考 企业资源最优配置标用途用途用途用途用途用途淘宝西邦考 容易犯淘宝西邦考 例子：部门资源的最优配 企企产品产产品产品产品淘宝西邦考 资源限制条 淘宝西邦考 部门的投入与 3个产品的净收益与投入的关系如产品 Q13（效率最低产品22Q22（效率中等产品 3Q31（效率最高淘宝西邦考 单一投资的收 3Q36 3946淘宝西邦考 最优的资源配达到最优 配置时 淘宝西邦考 配置问题小最 配置计算结果概括如下产品部123用净收收益边际收益淘宝西邦考 为什么需求曲线向下倾Theequimarginalprincipleperfectlyexplainswhydemandcurvesslope淘宝西邦考 AhigherpriceforagoodreducestheconsumerAhigherpriceforagoodreducestheconsumer’sdesiredconsumptionofthat淘宝西邦考 Px><Px><=TrytofillthetheemptyboxescorrectlywitheitheranequalsTrytofillthetheemptyboxescorrectlywitheitheranequalssign,agreaterthansign,oralessthansign.><=consumemoreofgoodxconsumemoreofgoodz淘宝西邦考 正确的回>consumemoreofgoodx<consumemoreofgoodz淘宝西邦考 闲暇和最优配Thesameruleof umutilityperhourcanbeappliedtomanydifferentareasoflife.UUrUeItisnotamerelyalawofeconomicsItisalawofrationalchoice(理性选择).淘宝西邦考 替代效应和收入效淘宝西邦考 选择性的方Overthelastfewdecades,economistshavedevelopedanalternativeapproach(方法)to ysisofdemand—onethatmakesnomentionofmarginalThisalternativeapproachindifferencecurves无差异曲线torigorouslyandconsistently严格和一致地)producethemajorpropositionsaboutconsumer淘宝西邦考 替代效Thefirstfactorexplaining demandcurveisthesubstitutioneffect(替代效应).Thesubstitutioneffectsaysthatwhenthepriceofagoodrises,consumerswilltendtosubstituteothergoodsforthemoreexpensivegoodinordertosatisfytheirdesiresmoreinexpensively.淘宝西邦考 收入效Thesecondfactorexplaining demandcurveisthe eeffect eeffectdenotestheimpactofapricechangeonagood’s demandedthatresultfromtheeffectofthepricechangeonconsumes’real淘宝西邦考 名义收入和实际收Wehavetounderstandthedifferencebetweennominal e(名义收入)and e(实际收入). eisthefacevalueofwhatwehaveinourpocketorbankaccount. esignifiestheactualamountofgoodsandservicesthatyour canbuy.淘宝西邦考 市场需淘宝西邦考 替代品和互补Goodsaresubstitutes(替代品)ifanincreaseinthepriceofoneincreasesthedemandfortheother.Goodsarecomplements(互补品)ifanincreaseinthepriceofonedecreasesthedemandfortheother.Goodsareindependent(无关的ifapricechangeforonehasnoeffectonthedemandfortheother.淘宝西邦考 一些物品的需求价格弹PriceGreenLegalgambling(合法Legalservice法律服务Medicalinsurance医疗保险Bustravel公共交通Residentialelectricty( 价格弹性和替代Thegreaterthenumberofsubstitutesforagood,themoreelasticitsdemandwillbe.Beefhasalotofsubstitutespoultry家禽),fish,andsoyproducts(豆制品).Incontrast,crack ehaslittleornoThat’swhyadrugaddict’s( demandismuchmoreinelasticthanabeefeater’s.淘宝西邦考 产品定Inthisregard,theelasticityofdemandalsodependsonhownarrowlytheproductisdefined.Forexample,whichdoyouthinkhasamoreelasticdemand–Chevrongasor淘宝西邦考 例ThedemandforChevrongasismuchmoreelasticthanthedemandforgasbecausemanybrandssuchasS TexacocanbesubstitutedforChevron,butthereisnogoodsubstituteforgas.淘宝西邦考 收入弹 eelasticitydenotesthepercentagechangein tydemandeddividedbythepercentagechangeine,holdingotherthings,suchasprice,constant.

(Q+Q (I+I 淘宝西邦考 一些物品的收入弹eOwner-occupiedhousing私有住宅Restaurantmeals餐馆饮食Physiciansservices就医Pig 淘宝西邦考 按收入弹性的物品分Normalgoods正常品EisareInferiorgoods劣等品EisareNecessities必需品EisarepositivebutLuxuries奢侈品Eisare淘宝西邦考 经济Anaddictivesubstance(上瘾品)isoneforwhichthedesiretoconsumedependssignificantlyonpastconsumption.Bycontrast,forconventionaldemandstodayarenotlikelytodependsodirectlyonconsumptionpatterns消费模式)yesterday.淘宝西邦考 重度成瘾者的需DManyofthePriceof (illegaldrugsPriceofofillegaldrugsfromthe (legaldrugs)ofSsubstancesratherSfrom tyofaddictive淘宝西邦考 偶尔染毒者的需 PriceofPriceofS

RaisingthepricesofharmfulsubstancescanSreducetheS(legaldrugs)ofcasualuserswillbeDictive

intothe淘宝西邦考 种 控制和预防统计，当政期间，的产量下降了94%。因为的产量映为市场生价格的变动：2000年每公斤生价值为30，2001年飞涨到300，到9月初，随着量下降，一公斤生已经卖到700 年月日A20淘宝西邦考 全球 来 《 报告》 上一年的增幅达到64％，不过因为当年天气偏冷，产量只增加17％，即生产鸦 的87％）。而 人口，在卡尔扎 。 淘宝西邦考 水与钻石悖AdamSmithposedtheparadox悖论，似非而是的论点)ofvalue:Nothingisusefulthanwater;butitwillscarcepurchaseanything.Adiamond,onthecontrary,hasscarceanyvalueinuse;butaverygreat tyofothergoodsmayfrequentlybeinexchangeforit.淘宝西邦考 价值悖TheThetotalutilityfromwaterconsumptiondoesnotdetermineitspriceordemand.Rather,water’spriceisdeterminedbyitsmarginalutility,bytheusefulnessofthelastglassofwater.淘宝西邦考 消费者剩Thegapbetweenthetotalutilityofagoodanditstotalmarketvalueiscalledconsumersurplus(消费者剩余Becauseofdiminishingmarginalconsumer’ssatisfactionexceedswhatis淘宝西邦考 消费者剩余图需求曲价 消需求曲价淘宝西邦考

数 市场的消费者剩Priceandmarginalutilityoftyof

Price

淘宝西邦考 附消费者均衡的几何分（可以选择第77页的内容淘宝西邦考 无差异曲Supposeaconsumerbuysdifferentcombinationsoftwocommodities,say,foodandclothing,atagivensetofprice.IfyouwereaskedtochoosebetweencombinationAandcombinationB,youmight(1)preferAtoB,(2)preferBtoA,(3)bedifferentbetweenAand淘宝西邦考 背景知淘宝西邦考 ABCD一个消费者的无差异ABCD

A16B23C32D4淘宝西邦考 替代法Thescarceragood,thegreateritsrelativesubstitutionThescarceragood,thegreateritsrelativesubstitutionvalue;itsmarginalutilityrisesrelativetothemarginalutilityofthegoodthathas 3 1

淘宝西邦考 替代 MUC×△C=MUFCD

===oo西邦考 无差异曲线AFamilyofIndifferenceCurves(无差异曲线簇):CurveU4standsforahigherlevelofsatisfactionthanU3;U3forahigherlevelofsatisfactionthanU2;andsoforth.oo淘宝西邦考 预算线和预算约Consumer’sM40323M403231N0642

淘宝西邦考 PC×△C=PF =

= 2

淘宝西邦考 =B==B=oo淘宝西邦考 BB‖收入变BB‖Fo NB‖

单纯价格变Ariseinthepriceoffoodmakesbudgetlinepivot(绕…转)onN.ThenewtangencyequilibriumisatB‖