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

ConsumerChoiceTheory,Chapter4,Content,4.1Utility,4.2CardinalUtility,4.3OrdinalUtility,Astory: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？,4.1Utility,4.1.1DefinitionofUtilityUtilityThebenefitorsatisfactionthatapersongetsfromtheconsumptionofagoodorservice（消费者在消费商品时所感受到的满足程度）Utilityispeoplessubjectivefeeling,4.1.2Thetheoryofutility,4.2CardinalUtility（基数效用）,4.2.1IntroductionofCardinalUtility,e.g.Theutilityofanewclothis100units,theutilityofasteakis50units,thenthetotalutilityofthisshoppingis150units,Utilitygenerallyincreasesasthequantityconsumedofagoodincrease（效用是消费量的函数）,U=f（Q1，Q2，Qn）,MarginalUtilityAnalysis,Cardinalutility:Utilitycanbeexpressedbycardinalnumberanddirectlymeasuredandsummed（效用可以用基数表示，可以直接计量并加总求和）,4.2.2TotalUtilityandMarginalUtility,TotalUtility(TU):ThetotalbenefitthatapersongetsfromtheconsumptionofagoodorserviceTU=f（Q）,MarginalUtility(MU/边际效用):Thechangeintotalutilitythatresultsfromaone-unitincreaseinthequantityofagoodconsumedMU=TU/Q,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,TheRelationshipbetweenTUandMU（重要！总效用和边际效用的关系）,TU,Q,TU,MU,Q,WhenMU0,TU;,MU,P,P,WhenMU(MUy/Py),buymoreXandlessY,andviceverse(whenallthebudgethasbeenspent),Application:FindingtheDemandCurve,DemandPrice: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,DemandpriceUtility-maximizingruleforonlyonegood:MU/P=,Q,P,Q=f（P）,DemandPrice,ActualPrice,ConsumerSurplus:Themaximumpricethatpeoplearewillingtopayforanotherunitofagoodminusthepricepaidforit（消费者愿意支付的价格实际支付的价格）,P0,Q0,Application:ConsumerSurplus（消费者剩余）,Q1,P1,ExerciseanHomework,1、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）,4.3.1IntroductionofOrdinalUtility,e.g.Consumercannotcalculatetheutilityofaclothorasteakbyacertainnumber,butcanaccuratelyjudgewhichoneheprefers,IndifferenceCurveAnalysis,Utilityisapsychologicalphenomenon,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）,Completeness,Transferability,Unsaturation,Consumercanalwayscompareandarrangeallthedifferentcombinationsofgoods,Thepreference:AB,andBC,thentheremustbeAC,Consumeralwayspreferthecombinationsthatcontainmoregoodstothosethatcontainlessgoods,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）,Y,X,I,Onthesamecurve,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）,NegativeSlope,Cannotintersect,Prefertherightone,Theindifferencecurveisdownward-slopingThequantityconsumedofonegoodmustincreasewhilethequantityconsumedoftheotheronedecreasingsothatthetotalutilitycanremainthesame,Therearecountlessindifferencecurvesonthemap,eachonerepresentadifferentutility,andthefartherawayfromtheorigin,thegreatertheutilityis,Theindifferencecurvesonthesamemapareparalleltoeachother,otherwiseitwillconflictwiththeabove,FeaturesoftheIndifferenceCurve,Convextotheorigin,Theabsolutevalueofslopeisdiminishing（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)andatthesametimeremainonthesameindifferencecurve（在维持效用水平不变的前提下，消费者增加一单位商品X的消费量时所需放弃的商品Y的消费量）Absolutevalueoftheslopeofacertainpointontheindifferencecurve（边际替代率是无差异曲线上某个点的斜率的绝对值）,MarginalRateofSubstitution(MRS)Animportantrelationship:Diminishingmarginalrateofsubstitution（边际替代率递减）WithacontinuousincreaseinthequantityconsumedofgoodX,thequantityofgoodYthattheconsumershouldgiveuptogetonemoreunitofXisdecreasing(remainonthesameindifferencecurve)（在维持效用水平不变的前提下，随着商品X的消费量连续增加，消费者为得到每一单位的商品X所需要放弃的商品Y的消费量是递减的）,4.3.3ConsumptionPossibilities（消费可能性）,TheBudgetLine（预算线）:Alinethatdescribesthelimitstoconsumptionchoiceswhichdependsonaconsumersbudgetandthepricesofgoods,PointA:SpendallthebudgetonX（全买X）PointB:SpendallthebudgetonY（全买Y）PointC:CanaffordandhavesomeunspentbudgetPointD:Cannotafford,Eachpointonthebudgetlinerepresentadifferentcombinationoftwogoodsandthecostofeachcombinationequalstoeachother（购买曲线上每个点所花的钱相等）,ChangesinPrices,Y,X,X,Y,PriceofXfalls,PriceofXrises,PriceofYfalls,PriceofYremainthesame,PriceofYrises,PriceofXremainthesame,PricesremainthesameBudget，BudgetLineBudget，BudgetLine,ChangeintheBudget,ThebudgetremainthesameDecreasesofpriceswithproportionshiftthebudgetlinerightwardIncreasesofpriceswithproportionshiftthebudgetlinerightward,4.3.4ConsumerEquilibrium（消费者均衡）,A&B:lessutility,unspentbudgetD:largeutilitybutcantaffordE(pointofcontact切点):bestaffordablepoint,Buytheaffordablequantitiesofgoods（钱花光）Aswelloffaspossible（获得最大满足）Theconsumersgoal:Allocatingthebudgetinawaytogetontothehighestattainableindifferencecurve（尽量达到更高的无差异曲线）,MRSXY=PX/PY(Equalslopeatthepointofcontact),4.3.5SubstitutionEffectsandIncomeEffects,Theinfluencesonthepriceofdemandfallintotwogroups:SubstitutioneffectsIncomeeffects,RelativePriceThepriceofonegoodintermsofanothergoodItequalsthepriceofonegooddividedbythepriceofanothergoodTheabsolutevalueoftheslopeofbudgetlineistherelativeprice,4.3.5SubstitutionEffectsandIncomeEffects,SubstitutionEffects,TheeffectoftherelativepricechangeWhenthepriceofgoodXfalls,therelativepriceofgoodXandgoodYchanges,XturnstobecheaperandYbecomesmoreexpensive,sotheconsumerwillchooseanewcombinationwhichcontainsmoreXandlessY,IncomeEffects,TheeffectduetoincomehavingbeenfreedupWhenthepriceofgoodXfalls,theconsumercanaffordmoreXwhilethebudgetremainsthesame,itlooksliketheincomeincrease,5、替代效应和收入效应,价格引起需求量变化是替代效应和收入效应共同作用的结果,替代效应,收入效应,商品1降价，相对于商品2更便宜，消费者会增加商品1的购买量而减少商品2的购买量，即商品1替代了商品2,商品1降价，相同货币的实际购买力增强，相当于实际收入水平增加，消费者会改变两种商品的购买量，以获得更大的效用,总效应,价格变动引起相对价格变动，进而引起需求量变动不改变效用水平,价格变动引起实际收入水平变动，进而引起需求量变动效用水平会改变,NormalGoods,Thesubstitution:ThequantityconsumedofXincreasewhenthepriceofXfallsTheincomeeffect:ThequantityconsumedofXincreasewhenthepriceofXfallsThequantityconsumedofXincreasewhenthepriceofXfalls,X,C,b,X3,F,G,U2,c,B,X2,TotalEffect,SubstitutionEffect,IncomeEffect,正常品的替代效应和收入效应,替代效应和收入效应均使消费量与价格反方向变动，从而总效应必然使消费量与价格反方向变动，需求曲线向右下倾斜,X,C,b,X3,F,G,U2,c,B,X2,补偿预算线,总效应,替代效应,收入效应,InferiorGoods,Y,0,X,B,a,X1,b,X3,F,G,U1,U2,c,X2,TotalEffect,SubstitutionEffect,IncomeEffect,Thesubstitutioneffect:ThequantityconsumedofXincreasewhenthepriceofXfallsTheincomeeffect:ThequantityconsumedofXdecreasewhenthepriceofXfallsThesubstitutioneffectisgreaterthantheincomeeffectThequantityconsumedofXincreasewhenthepriceofXfalls,一般低档品的替代效应和收入效应,替代效应使消费量与价格反方向变动，收入效应使消费量与价格同方向变动，通常收入效应小于替代效应，故总效应使消费量与价格反方向变动，需求曲线向右下倾斜,X2,0,X1,B,a,X1,b,X1,F,G,U1,U2,c,X1,补偿预算线,总效应,替代效应,收入效应,GiffenGoods,0,X,Y,B,A,B,a,X1,b,X3,F,G,U1,U2,c,X2,TotalEffect,SubstitutionEffect,IncomeEffect,Thesubstitutioneffect:ThequantityconsumedofXincreasewhenthepriceofXfallsTheincomeeffect:Thequa