微观经济学-双语课件-第4章-消费者行为理论-CH4-Consumer-Choice-Theory

ConsumerChoiceTheoryChapter4Content4.1Utility4.2CardinalUtility4.3OrdinalUtilityAstory:珍珠翡翠白玉汤明太祖朱元璋从前是个乞丐，传说他有次在路上饿晕，被好心人救回家中，用豆腐块、菠菜、剩米饭煮成汤给朱元璋吃。朱元璋食后，精神大振，问刚才吃的是什么，回答说“珍珠翡翠白玉汤”。后来，朱元璋当上了皇帝，尝尽了天下美味，突然就想起了“珍珠翡翠白玉汤”的美味，当即下令御厨做给他吃。谁知御厨照着皇上的描述做好了汤，朱元璋尝后，却觉得根本不对味。又传在八国联军侵华之时，慈禧太后被迫西逃，路上又累又饿，在一户平民家里歇脚。主人没有什么好吃的，就把小米拌上少量白面做成面颗粒，倒入菠菜豆腐汤内。慈禧太后吃着觉得非常美味，问及汤名，答曰“珍珠翡翠白玉汤”，慈禧太后龙颜大悦。后来慈禧太后回宫，专门派御厨学做此汤，没想到再次吃上时，却怎么也吃不出当初在荒郊村野的平民家里那个香味了。Thinking珍珠翡翠白玉汤的传说说明了什么道理？4.1Utility4.1.1DefinitionofUtilityUtilityThebenefitorsatisfactionthatapersongetsfromtheconsumptionofagoodorservice（消费者在消费商品时所感受到的满足程度）Utilityispeople'ssubjectivefeeling4.1.2Thetheoryofutility4.2CardinalUtility（基数效用）4.2.1IntroductionofCardinalUtilitye.g.Theutilityofanewclothis100units,theutilityofasteakis50units,thenthetotalutilityofthisshoppingis150unitsUtilitygenerallyincreasesasthequantityconsumedofagoodincrease（效用是消费量的函数）U=f（Q1，Q2，…，Qn）MarginalUtilityAnalysisCardinalutility:Utilitycanbeexpressedbycardinalnumberanddirectlymeasuredandsummed（效用可以用基数表示，可以直接计量并加总求和）4.2.2TotalUtilityandMarginalUtilityTotalUtility(TU):ThetotalbenefitthatapersongetsfromtheconsumptionofagoodorserviceTU=f（Q）MarginalUtility(MU/边际效用):Thechangeintotalutilitythatresultsfromaone-unitincreaseinthequantityofagoodconsumedMU=ΔTU/ΔQ,MU==dTU/dQ除了边际效用之外，后面我们还要用到其他很多“边际值”，每一个边际值都代表着对应总量的增量，即总量的某个影响因素变动1个单位时，引起总量变动了几个单位小贴士QuantityTUMU0001303025020360104600550-10TheRelationshipbetweenTUandMU（重要！总效用和边际效用的关系）TUQTUMUQWhenMU0,TU↑;MUPP’WhenMU0,TU↓;WhenMU=0,TUreachesthemaximum4.2.3LawofDiminishingMarginalUtility边际效用递减：随着对某种商品消费量的增加，人们从该商品连续增加的消费单位中得到的满足程度逐渐下降ThegeneraltendencyformarginalutilitytodecreaseasthequantityofagoodconsumedincreasesQMUP’4.2.4ConsumerEquilibrium（消费者均衡）ThisoutcomeoccurswhenapersonfollowstheUtility-maximizingRule（效用最大化原则）Allocatetheentireavailablebudget（所有预算全花光）Makethemarginalutilityperdollarspentthesameforallgoods（使花费在各种商品购买上的最后一元钱所带来的边际效用相等，即：各商品的边际效用与价格之比相等）ConsumerEquilibrium:ThegoalofaconsumeristoallocatetheavailablebudgetinawaythatmaximizestotalutilityTowkindsofGoodsI:Income(orBudget)Px:PriceofGoodXPy:PriceofGoodYQx:QuantityconsumedofXQy:QuantityconsumedofYMUx:MarginalUtilityofXMUy:MarginalUtilityofYλ:UtilityofOneDollaryyxxyyxxPMUPMUIQPQPExampleAconsumerallocates$8betweenappleandpearwhenthepriceofappleis$1andthepriceofpearis$2,thenwhichcombinationofappleandpearcanleadstothegreatesttotalutility?Q12345678MUapple1110987654MUpear19161513121086Animportantrule:If(MUx/Px)(MUy/Py),buymoreXandlessY,andviceverse(whenallthebudgethasbeenspent)Application:FindingtheDemandCurveDemandPrice:Themaximumpricethataconsumeriswillingtopayforagivenquantityofagoodduringaspecifiedperiod(需求价格：消费者在一定时期内对一定量的某种商品所愿意支付的最高价格)Demandpricedependsonmarginalutility:MU↑,Demandprice↑Utility-maximizingruleforonlyonegood:MU/P=λQMUλ=2P13015220103105400051015201234QPQ=f（P）DemandPriceActualPriceConsumerSurplus:Themaximumpricethatpeoplearewillingtopayforanotherunitofagoodminusthepricepaidforit（消费者愿意支付的价格–实际支付的价格）P0Q0Application:ConsumerSurplus（消费者剩余）Q1P1ExerciseanHomework1、当总效用曲线达到顶点时，（）A、边际效用为最大值B、边际效用为零C、边际效用为正D、边际效用为负2、消费者剩余是（）A、消费过剩的商品B、消费者得到的总效用C、消费者买商品所得到的总效用减去支出的货币的总效用D、支出的货币的总效用3、已知消费者收入为100元，商品X的价格是10元，商品Y的价格是3元。假定他打算购买7单位X和10单位Y，此时X和Y的边际效用分别是50和18，如要获得最大效用，他应该（）A、停止购买B、减少X的购买量，增加Y的购买量C、增加X的购买量，减少Y的购买量D、同时增加X和Y的购买量4、消费者剩余是消费者的（）A、实际所得B、主观感受C、没有购买的部分D、消费剩余的部分5、钻石用处极小但价格昂贵，而生活中必不可少的水却价格便宜，请用边际效用的概念予以解释4.3OrdinalUtility（序数效用）4.3.1IntroductionofOrdinalUtilitye.g.Consumercannotcalculatetheutilityofaclothorasteakbyacertainnumber,butcanaccuratelyjudgewhichoneheprefersIndifferenceCurveAnalysisUtilityisapsychologicalphenomenon,itcannotbemeasuredorsummedup,wecanonlyshowthelevelofsatisfactionwiththeorder（效用作为一种心理现象无法计量，也不能加总求和，只能表示出满足程度的高低与顺序）4.3.2IndifferenceCurves（无差异曲线）Assumptionsforpreference（关于偏好的假设）CompletenessTransferabilityUnsaturationConsumercanalwayscompareandarrangeallthedifferentcombinationsofgoodsThepreference:AB,andBC,thentheremustbeACConsumeralwayspreferthecombinationsthatcontainmoregoodstothosethatcontainlessgoods完全性可传递性非饱和性IndifferenceCurve（无差异曲线）Alinethatshowscombinationsofgoodsamongwhichaconsumerisindifferent(thatmeanstheconsumerlikeallthecombinationsequally)（无差异曲线表示消费者偏好相同的两种商品的所有组合）YXIOnthesamecurve,theutilityofeachcombinationequalstheothers（线上任何一点X与Y的不同组合，给消费者所带来的效用相同）NegativeSlopeCannotintersectPrefertherightone•Theindifferencecurveisdownward-sloping•ThequantityconsumedofonegoodmustincreasewhilethequantityconsumedoftheotheronedecreasingsothatthetotalutilitycanremainthesameTherearecountlessindifferencecurvesonthemap,eachonerepresentadifferentutility,andthefartherawayfromtheorigin,thegreatertheutilityisTheindifferencecurvesonthesamemapareparalleltoeachother,otherwiseitwillconflictwiththeaboveFeaturesoftheIndifferenceCurveConvextotheoriginTheabsolutevalueofslopeisdiminishing（斜率的绝对值递减）斜率为负同一平面上越靠右的曲线代表的效用越大任意两条不相交凸向原点MarginalRateofSubstitution(MRS)TherateatwhichapersonwillgiveupgoodY(thegoodmeasuredonthey-axis)togetmoreofgoodX(thegoodmeasuredonthex-axis)andatthesametimeremainonthesameindiffe