《微观经济学》清华大学课件Ch9BuyingandSelling

ChapterNineBuyingandSellingChapterNineBuyingandSelling1WhatAreWeDoinginthisChapter?

Weexpandourbasicconsumerchoiceframeworktoincludethepossibilitythatconsumerscansellsomethingtogenerateincome.Again,intermsoftheoreticalframework,nothingisnew.WhatAreWeDoinginthisChap2Endowments禀赋Thelistofresourceunitswithwhichaconsumerstartsishisendowment.Aconsumer’sendowmentwillbedenotedbythevector(omega).Endowments禀赋Thelistofresou3EndowmentsE.g.

statesthattheconsumerisendowedwith10unitsofgood1and2unitsofgood2.Whatistheendowment’svalue?Forwhichconsumptionbundlesmayitbeexchanged?EndowmentsE.g.

statesthatthe4BudgetConstraintsRevisitedSo,givenp1andp2,thebudgetconstraintforaconsumerwithanendowmentis

ThebudgetsetisBudgetConstraintsRevisitedSo5BudgetConstraintsRevisitedx2x1w1w2BudgetsetBudgetConstraintsRevisitedx26BudgetConstraintsRevisitedx2x1w1w2BudgetsetBudgetConstraintsRevisitedx27BudgetConstraintsRevisitedx2x1w1w2Theendowmentpointisalwayson

thebudgetconstraint.Sopricechangespivotthe

constraintaboutthe

endowmentpoint.BudgetConstraintsRevisitedx28BudgetConstraintsRevisitedTheconstraint

is

Thatis,thesumofthevaluesofaconsumer’snetdemandsiszero.BudgetConstraintsRevisitedTh9NetDemandsx2x1w1w2x2*x1*Atprices(p1,p2)theconsumer

sellsunitsofgood1toacquire

moreunitsofgood2.NetDemandsx2x1w1w2x2*x1*Atpr10NetDemandsx2x1x2*=w2x1*=w1Atprices(p1”,p2”)theconsumer

consumesherendowment;net

demandsareallzero.NetDemandsx2x1x2*=w2x1*=w1At11NetDemandsx2x1w1w2Price-offercurvecontainsallthe

utility-maximizinggrossdemands

forwhichtheendowmentcanbe

exchanged.NetDemandsx2x1w1w2Price-offer12AVariationoftheTheme:IncomefromLaborAworkerisendowedwith$mofnonlaborincomeandRhoursoftimewhichcanbeusedforlabororleisure.w=(R,m).Consumptiongood’spriceispc.wisthewagerate.¾¾AVariationoftheTheme:Inc13LaborSupplyTheworker’sbudgetconstraintis

whereC,Rdenotegrossdemandsfortheconsumptiongoodandforleisure.Thatis¾¾{{endowment

valueexpenditureLaborSupplyTheworker’sbudge14LaborSupplyCRR¾endowmentm($)LaborSupplyCRR¾endowmentm($)15LaborSupplyCRR¾endowment¾¾mLaborSupplyCRR¾endowment¾¾m16LaborSupplyCRR¾endowment¾¾mslope=,the‘realwagerate’LaborSupplyCRR¾endowment¾¾msl17LaborSupplyCRR¾endowment¾¾mC*R*leisure

demandedlabor

suppliedLaborSupplyCRR¾endowment¾¾mC*18TheMoraleoftheStory:LimitedPossibilityofMarketTransactionsTherearesomecasesinwhichagoodcannotbesoldorboughtinanyamount!TheMoraleoftheStory:Limi19Slutsky’sEquationRevisitedSlutsky:changestodemandscausedbyapricechangearethesumofapuresubstitutioneffect,andanincomeeffect.Thisassumedthatincomeydidnotchangeaspriceschanged.But

doeschangewithprice.HowdoesthismodifySlutsky’sequation?Slutsky’sEquationRevisitedSl20Slutsky’sEquationRevisitedAchangeinp1orp2changes

sotherewillbe

anadditionalincomeeffect,calledtheendowmentincomeeffect.Slutsky’sdecompositionwillthushavethreecomponentsapuresubstitutioneffectan(ordinary)incomeeffect,andanendowmentincomeeffect.Slutsky’sEquationRevisitedA21Slutsky’sEquationRevisitedx1w2w1x2x2’x1’Initialpricesare(p1’,p2’).Slutsky’sEquationRevisitedx122Slutsky’sEquationRevisitedx1w2w1x2x2’x1”x2”Initialpricesare(p1’,p2’).

Finalpricesare(p1”,p2”).Howisthechangeindemand

from(x1’,x2’)to(x1”,x2”)explained?x1’Slutsky’sEquationRevisitedx123Slutsky’sEquationRevisitedx1w2w1x2x2’x1’Initialpricesare(p1’,p2’).Slutsky’sEquationRevisitedx124Slutsky’sEquationRevisitedx1w2w1x2x2’x1”x2”Initialpricesare(p1’,p2’).

Finalpricesare(p1”,p2”).x1’Slutsky’sEquationRevisitedx125Slutsky’sEquationRevisitedx1w2w1x2PuresubstitutioneffectÞSlutsky’sEquationRevisitedx126Slutsky’sEquationRevisitedx1w2w1x2PuresubstitutioneffectÞSlutsky’sEquationRevisitedx127Slutsky’sEquationRevisitedx1w2w1x2PuresubstitutioneffectÞOrdinaryincomeeffectÞSlutsky’sEquationRevisitedx128Slutsky’sEquationRevisitedx1w2w1x2PuresubstitutioneffectÞOrdinaryincomeeffectÞSlutsky’sEquationRevisitedx129Slutsky’sEquationRevisitedx1w2w1x2PuresubstitutioneffectÞOrdinaryincomeeffectÞEndowmentincomeeffectÞSlutsky’sEquationRevisitedx130Slutsky’sEquationRevisitedx1w2w1x2PuresubstitutioneffectÞOrdinaryincomeeffectÞEndowmentincomeeffectÞSlutsky’sEquationRevisitedx131Slutsky’sEquationRevisitedOverallchangeindemandcausedbya

changeinpriceisthesumof:(i)apuresubstitutioneffect(ii)anordinaryincomeeffect(iii)anendowmentincomeeffectSlutsky’sEquationRevisitedOv32一个经典例子

白居易《卖炭翁》

……

可怜身上衣正单，

心忧炭贱愿天寒。

……一个经典例子

白居易《卖炭翁》

……

可怜身上衣正单，33ChapterNineBuyingandSellingChapterNineBuyingandSelling34WhatAreWeDoinginthisChapter?

Weexpandourbasicconsumerchoiceframeworktoincludethepossibilitythatconsumerscansellsomethingtogenerateincome.Again,intermsoftheoreticalframework,nothingisnew.WhatAreWeDoinginthisChap35Endowments禀赋Thelistofresourceunitswithwhichaconsumerstartsishisendowment.Aconsumer’sendowmentwillbedenotedbythevector(omega).Endowments禀赋Thelistofresou36EndowmentsE.g.

statesthattheconsumerisendowedwith10unitsofgood1and2unitsofgood2.Whatistheendowment’svalue?Forwhichconsumptionbundlesmayitbeexchanged?EndowmentsE.g.

statesthatthe37BudgetConstraintsRevisitedSo,givenp1andp2,thebudgetconstraintforaconsumerwithanendowmentis

ThebudgetsetisBudgetConstraintsRevisitedSo38BudgetConstraintsRevisitedx2x1w1w2BudgetsetBudgetConstraintsRevisitedx239BudgetConstraintsRevisitedx2x1w1w2BudgetsetBudgetConstraintsRevisitedx240BudgetConstraintsRevisitedx2x1w1w2Theendowmentpointisalwayson

thebudgetconstraint.Sopricechangespivotthe

constraintaboutthe

endowmentpoint.BudgetConstraintsRevisitedx241BudgetConstraintsRevisitedTheconstraint

is

Thatis,thesumofthevaluesofaconsumer’snetdemandsiszero.BudgetConstraintsRevisitedTh42NetDemandsx2x1w1w2x2*x1*Atprices(p1,p2)theconsumer

sellsunitsofgood1toacquire

moreunitsofgood2.NetDemandsx2x1w1w2x2*x1*Atpr43NetDemandsx2x1x2*=w2x1*=w1Atprices(p1”,p2”)theconsumer

consumesherendowment;net

demandsareallzero.NetDemandsx2x1x2*=w2x1*=w1At44NetDemandsx2x1w1w2Price-offercurvecontainsallthe

utility-maximizinggrossdemands

forwhichtheendowmentcanbe

exchanged.NetDemandsx2x1w1w2Price-offer45AVariationoftheTheme:IncomefromLaborAworkerisendowedwith$mofnonlaborincomeandRhoursoftimewhichcanbeusedforlabororleisure.w=(R,m).Consumptiongood’spriceispc.wisthewagerate.¾¾AVariationoftheTheme:Inc46LaborSupplyTheworker’sbudgetconstraintis

whereC,Rdenotegrossdemandsfortheconsumptiongoodandforleisure.Thatis¾¾{{endowment

valueexpenditureLaborSupplyTheworker’sbudge47LaborSupplyCRR¾endowmentm($)LaborSupplyCRR¾endowmentm($)48LaborSupplyCRR¾endowment¾¾mLaborSupplyCRR¾endowment¾¾m49LaborSupplyCRR¾endowment¾¾mslope=,the‘realwagerate’LaborSupplyCRR¾endowment¾¾msl50LaborSupplyCRR¾endowment¾¾mC*R*leisure

demandedlabor

suppliedLaborSupplyCRR¾endowment¾¾mC*51TheMoraleoftheStory:LimitedPossibilityofMarketTransactionsTherearesomecasesinwhichagoodcannotbesoldorboughtinanyamount!TheMoraleoftheStory:Limi52Slutsky’sEquationRevisitedSlutsky:changestodemandscausedbyapricechangearethesumofapuresubstitutioneffect,andanincomeeffect.Thisassumedthatincomeydidnotchangeaspriceschanged.But

doeschangewithprice.HowdoesthismodifySlutsky’sequation?Slutsky’sEquationRevisitedSl53Slutsky’sEquationRevisitedAchangeinp1orp2changes

sotherewillbe

anadditionalincomeeffect,calledtheendowmentincomeeffect.Slutsky’sdecompositionwillthushavethreecomponentsapuresubstitutioneffectan(ordinary)incomeeffect,andanendowmentincomeeffect.Slutsky’sEquationRevisitedA54Slutsky’sEquationRevisitedx1w2w1x2x2’x1’Initialpricesare(p1’,p2’).Slutsky’sEquationRevisitedx155Slutsky’sEquationRevisitedx1w2w1x2x2’x1”x2”Initialpricesare(p1’,p2’).

Finalpricesare(p1”,p2”).Howisthechangeindemand

from(x1’,x2’)to(x1”,x2”)explained?x1’Slutsky’sEquationRevisitedx156Slutsky’sEquationRevisitedx1w2w1x2x2’x1’Initialpricesare(p1’,p2’).Slutsky’sEquationRevisitedx157Slutsky’sEquationRevisitedx1w2w1x2x2’x1”x2”Initialpricesare(p1’,p2’).

Finalpricesare(p1”,p2”).x1’Slutsky’sEquationRevisitedx158Slutsky