第5章-需求和消費者行為

需求與消費者行第5淘寶西邦考 選擇和效用理淘寶西邦考 消費者行Theconceptofindividualchoiceisoneofthemostimportantineconomics.Economicsrelaysonthefundamentalpremise(基本假定)thatpeopletendtochoosethosegoodsandservicestheyvaluemost淘寶西邦考 效用理Utilitydenotessatisfaction.Moreprecisely,itreferstohowconsumersrankdifferentgoodsandservices.Inthetheoryofdemand,wesaythat izetheirutility,whichmeansthattheychoosethebundleofconsumptiongoods消費品束thatmost淘寶西邦考 背景知識：邊1870s前期，英國的杰文斯、僑居的法國人瓦爾拉和奧地利的門格爾，三人發(fā)起“邊際”。WilliamS.Jevons

Léon

CarlMenger淘寶西邦考 邊際效用價值掀起邊際的學者用倡導并發(fā)揚“邊際效用價值論”，用效用價值論與當時的勞動價值論相對抗，以邊際分析方法取代當時的平均分析方法，因而成Marginalutilityistheadditionalutilityderivedfromaoneunitincreasein淘寶西邦考 總效用和邊際效消費數 （總）效 邊際效 淘寶西邦考 總效用和邊際效用的關Q i Q邊際效用遞減定Marginal Marginal西邦考 效用理論的歷DanielBernoulli伯努利amemberofabrilliantSwissfamilyofmathematicians,observedin1738thatpeopleactasifthedollartheystandtogaininafairbet賭)isworthlesstothemthanthedollartheystandtoThismeansthatsuccessive(連續(xù)的)newdollarsofwealthbringthemsmallerandsmallerincrements(增量)oftrueutility.淘寶西邦考 JeremyBentham

JeremyBentham(邊沁)proposedthatsocietyshouldbeorganizedontheprincipleofutility‖whichhedefinedasthe―prpertyproducepleasure,goodorhappinessortoprevent…pain,evilorunhappiness.‖淘寶西邦考 功利主義的觀Alllegislation( shouldbedesignedonutilitarianprinciples(功利原則)topromotetheeatesthappinessofthegreatestTheyevendevelopedameasureofpleasuretheycalledtheutil.淘寶西邦考 序數效Anordinal序數measuresimplyranksgoodsrelativetooneanother.Youcansayyoulikepeasbetterthanbroccoli花椰菜andyoulikeicecreambetterthanbothofthosevegetablesbutyoudon’treallyneedtosayhowmuchtorankyourpreferences(偏好)forthese淘寶西邦考 背景知淘寶西邦考 等邊際原淘寶西邦考 消費者的最優(yōu)Weassumethatconsumers utilitysubjecttoabudgetor Consumershaveacertainamountofetospendand,subjecttotheirbudgetconstraint預算約束andgivenofprices,theywillchooseabasketofgoodsthatwillprovidethemwiththegreatestutilityorsatisfaction.淘寶西邦考 問題：最優(yōu)支出原淘寶西邦考 簡化的例淘寶西邦考 衣服和食物123456789方案1：總效用8040120方案2：總效用≈10810118最優(yōu)方案淘寶西邦考 效用最大的開1234567898642654321用于衣服，總效用=98+27=125。問題：如果有16元錢，應該怎樣開淘寶西邦考 最優(yōu)開支判別方金1234567898642654321淘寶西邦考 最后（邊際）1元錢的效1i

×物i的邊際效1元收入增加的即1元錢可以=1元錢 ×1單位商品 淘寶西邦考 收入最優(yōu)花費的條件物品1的邊際效用1=物品2的邊際效用1 簡寫為以下資源配置最優(yōu)的等邊際物品1的邊際效用=物品2的邊際效用物品1的價格 物品2的價格

=淘寶西邦考 邊際不等時的改善方物品1的邊際效用

=物品物品移動1元，效用凈增物品物品增加1增加1元支效用增加減少1元支效用減少淘寶西邦考 等邊際原Utilityis izedwhenthemarginalutilityofthelastdollarspentoneachgoodisexactlythesameasthemarginalutilityofthelastdollarspentonanyothergood.Thisistheutility- izingruleortheequimarginalprinciple(效用最大化準則淘寶西邦考 企業(yè)資源最優(yōu)配置標用途用途用途用途用途用途淘寶西邦考 容易犯淘寶西邦考 例子：部門資源的最優(yōu)配 企企產品產產品產品產品淘寶西邦考 資源限制條 淘寶西邦考 部門的投入與 3個產品的凈收益與投入的關系如產品 Q13（效率最低產品22Q22（效率中等產品 3Q31（效率最高淘寶西邦考 單一投資的收 3Q36 3946淘寶西邦考 最優(yōu)的資源配達到最優(yōu) 配置時 淘寶西邦考 配置問題小最 配置計算結果概括如下產品部123用凈收收益邊際收益淘寶西邦考 為什么需求曲線向下傾Theequimarginalprincipleperfectlyexplainswhydemandcurvesslope淘寶西邦考 AhigherpriceforagoodreducestheconsumerAhigherpriceforagoodreducestheconsumer’sdesiredconsumptionofthat淘寶西邦考 Px><Px><=TrytofillthetheemptyboxescorrectlywitheitheranequalsTrytofillthetheemptyboxescorrectlywitheitheranequalssign,agreaterthansign,oralessthansign.><=consumemoreofgoodxconsumemoreofgoodz淘寶西邦考 正確的回>consumemoreofgoodx<consumemoreofgoodz淘寶西邦考 閑暇和最優(yōu)配Thesameruleof umutilityperhourcanbeappliedtomanydifferentareasoflife.UUrUeItisnotamerelyalawofeconomicsItisalawofrationalchoice(理性選擇).淘寶西邦考 替代效應和收入效淘寶西邦考 選擇性的方Overthelastfewdecades,economistshavedevelopedanalternativeapproach(方法)to ysisofdemand—onethatmakesnomentionofmarginalThisalternativeapproachindifferencecurves無差異曲線torigorouslyandconsistently嚴格和一致地)producethemajorpropositionsaboutconsumer淘寶西邦考 替代效Thefirstfactorexplaining demandcurveisthesubstitutioneffect(替代效應).Thesubstitutioneffectsaysthatwhenthepriceofagoodrises,consumerswilltendtosubstituteothergoodsforthemoreexpensivegoodinordertosatisfytheirdesiresmoreinexpensively.淘寶西邦考 收入效Thesecondfactorexplaining demandcurveisthe eeffect eeffectdenotestheimpactofapricechangeonagood’s demandedthatresultfromtheeffectofthepricechangeonconsumes’real淘寶西邦考 名義收入和實際收Wehavetounderstandthedifferencebetweennominal e(名義收入)and e(實際收入). eisthefacevalueofwhatwehaveinourpocketorbankaccount. esignifiestheactualamountofgoodsandservicesthatyour canbuy.淘寶西邦考 市場需淘寶西邦考 替代品和互補Goodsaresubstitutes(替代品)ifanincreaseinthepriceofoneincreasesthedemandfortheother.Goodsarecomplements(互補品)ifanincreaseinthepriceofonedecreasesthedemandfortheother.Goodsareindependent(無關的ifapricechangeforonehasnoeffectonthedemandfortheother.淘寶西邦考 一些物品的需求價格彈PriceGreenLegalgambling(合法Legalservice法律服務Medicalinsurance醫(yī)療保險Bustravel公共交通Residentialelectricty( 價格彈性和替代Thegreaterthenumberofsubstitutesforagood,themoreelasticitsdemandwillbe.Beefhasalotofsubstitutespoultry家禽),fish,andsoyproducts(豆制品).Incontrast,crack ehaslittleornoThat’swhyadrugaddict’s( demandismuchmoreinelasticthanabeefeater’s.淘寶西邦考 產品定Inthisregard,theelasticityofdemandalsodependsonhownarrowlytheproductisdefined.Forexample,whichdoyouthinkhasamoreelasticdemand–Chevrongasor淘寶西邦考 例ThedemandforChevrongasismuchmoreelasticthanthedemandforgasbecausemanybrandssuchasS TexacocanbesubstitutedforChevron,butthereisnogoodsubstituteforgas.淘寶西邦考 收入彈 eelasticitydenotesthepercentagechangein tydemandeddividedbythepercentagechangeine,holdingotherthings,suchasprice,constant.

(Q+Q (I+I 淘寶西邦考 一些物品的收入彈eOwner-occupiedhousing私有住宅Restaurantmeals餐館飲食Physiciansservices就醫(yī)Pig 淘寶西邦考 按收入彈性的物品分Normalgoods正常品EisareInferiorgoods劣等品EisareNecessities必需品EisarepositivebutLuxuries奢侈品Eisare淘寶西邦考 經濟Anaddictivesubstance(上癮品)isoneforwhichthedesiretoconsumedependssignificantlyonpastconsumption.Bycontrast,forconventionaldemandstodayarenotlikelytodependsodirectlyonconsumptionpatterns消費模式)yesterday.淘寶西邦考 重度成癮者的需DManyofthePriceof (illegaldrugsPriceofofillegaldrugsfromthe (legaldrugs)ofSsubstancesratherSfrom tyofaddictive淘寶西邦考 偶爾染毒者的需 PriceofPriceofS

RaisingthepricesofharmfulsubstancescanSreducetheS(legaldrugs)ofcasualuserswillbeDictive

intothe淘寶西邦考 種 控制和預防統(tǒng)計，當政期間，的產量下降了94%。因為的產量映為市場生價格的變動：2000年每公斤生價值為30，2001年飛漲到300，到9月初，隨著量下降，一公斤生已經賣到700 年月日A20淘寶西邦考 全球 來 《 報告》 上一年的增幅達到64％，不過因為當年天氣偏冷，產量只增加17％，即生產鴉 的87％）。而 人口，在卡爾扎 。 淘寶西邦考 水與鉆石悖AdamSmithposedtheparadox悖論，似非而是的論點)ofvalue:Nothingisusefulthanwater;butitwillscarcepurchaseanything.Adiamond,onthecontrary,hasscarceanyvalueinuse;butaverygreat tyofothergoodsmayfrequentlybeinexchangeforit.淘寶西邦考 價值悖TheThetotalutilityfromwaterconsumptiondoesnotdetermineitspriceordemand.Rather,water’spriceisdeterminedbyitsmarginalutility,bytheusefulnessofthelastglassofwater.淘寶西邦考 消費者剩Thegapbetweenthetotalutilityofagoodanditstotalmarketvalueiscalledconsumersurplus(消費者剩余Becauseofdiminishingmarginalconsumer’ssatisfactionexceedswhatis淘寶西邦考 消費者剩余圖需求曲價 消需求曲價淘寶西邦考

數 市場的消費者剩Priceandmarginalutilityoftyof

Price

淘寶西邦考 附消費者均衡的幾何分（可以選擇第77頁的內容淘寶西邦考 無差異曲Supposeaconsumerbuysdifferentcombinationsoftwocommodities,say,foodandclothing,atagivensetofprice.IfyouwereaskedtochoosebetweencombinationAandcombinationB,youmight(1)preferAtoB,(2)preferBtoA,(3)bedifferentbetweenAand淘寶西邦考 背景知淘寶西邦考 ABCD一個消費者的無差異ABCD

A16B23C32D4淘寶西邦考 替代法Thescarceragood,thegreateritsrelativesubstitutionThescarceragood,thegreateritsrelativesubstitutionvalue;itsmarginalutilityrisesrelativetothemarginalutilityofthegoodthathas 3 1

淘寶西邦考 替代 MUC×△C=MUFCD

===oo西邦考 無差異曲線AFamilyofIndifferenceCurves(無差異曲線簇):CurveU4standsforahigherlevelofsatisfactionthanU3;U3forahigherlevelofsatisfactionthanU2;andsoforth.oo淘寶西邦考 預算線和預算約Consumer’sM40323M403231N0642

淘寶西邦考 PC×△C=PF =

= 2

淘寶西邦考 =B==B=oo淘寶西邦考 BB‖收入變BB‖Fo NB‖

單純價格變Ariseinthepriceoffoodmakesbudgetlinepivot(繞…轉)onN.ThenewtangencyequilibriumisatB‖