北大中级微观经济学课件ch.ppt

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1、Chapter NineBuying and Selling购买和销售购买和销售StructureuEndowments（禀赋）禀赋）uBudget constraints with endowmentsuNet demandsPrice offer curveuExample:Labor supplyComparative staticsuSlutsky equation revisitedBuying and SellinguTrade involves exchange-when something is bought something else must be sold.uWhat

2、will be bought?What will be sold?uWho will be a buyer?Who will be a seller?Buying and SellinguAnd how are incomes generated?uHow does the value of income depend upon commodity prices?uHow can we put all this together to explain better how price changes affect demands?EndowmentsuThe list of resource

3、units with which a consumer starts is his endowment（禀赋）禀赋）.uA consumers endowment will be denoted by the vector (omega).EndowmentsuE.g.states that the consumer is endowed with 10 units of good 1 and 2 units of good 2.uWhat is the endowments value?uFor which consumption bundles may it be exchanged?En

4、dowmentsup1=2 and p2=3 so the value of the endowment isuQ:For which consumption bundles may the endowment be exchanged?uA:For any bundle costing no more than the endowments value.Budget Constraints RevisiteduSo,given p1 and p2,the budget constraint for a consumer with an endowment isuThe budget set

5、is Budget Constraints Revisitedx2x1w w1 1w w2 2Budget Constraints Revisitedx2x1w w1 1w w2 2Budget setChanging Endowmentsx2x1(w1,w2)(w1”,w2”)(w1,w2)Changing the endowmentChanging Pricesx2x1w w1 1w w2 2Changing prices of the endowmentChanging Pricesx2x1w w1 1w w2 2Budget setChanging Pricesx2x1w w1 1w

6、w2 2The endowment point is always on the budget constraint.So price changes pivot theconstraint about the endowment point.Net DemanduThe constraintisuThat is,the sum of the values of a consumers net demands（净需求）净需求）is zero.Net DemandsuSuppose and p1=2,p2=3.Then the constraint is uIf the consumer gro

7、ss demands(毛需毛需求）求）(x1*,x2*)=(7,4),then 3 good 1 units exchange for 2 good 2 units.Net demands are x1*-w w1=7-10=-3 andx2*-w w2=4-2=+2.Net Demandsp1=2,p2=3,x1*-w w1=-3 and x2*-w w2=+2 soThe purchase of 2 extra good 2 units at$3 each is funded by giving up 3 good 1 units at$2 each.Net Demands at Diff

8、erent Pricesx2x1w w1 1w w2 2x2*x1*At prices(p1,p2)the consumersells units of good 1 to acquiremore units of good 2.Net seller of good 1x2x1w w1 1w w2 2x2*x1*At prices(p1,p2)the consumersells units of good 2 to acquiremore of good 1.Net buyer of good 1Net Demands at Different Pricesx2x1x2*=w w2 2x1*=

9、w w1 1At prices(p1”,p2”)the consumerconsumes her endowment;netdemands are all zero.AutarkyNet Demands at Different PricesOffer Curvex2x1w w1 1w w2 2Price-offer curve contains all theutility-maximizing gross demands for which the endowment can be exchanged.Net Demandsx2x1w w1 1w w2 2Price-offer curve

10、Sell good 1,buy good 2Net Demandsx2x1w w1 1w w2 2Price-offer curveBuy good 1,sell good 2因课件太大，无法上传。本处删因课件太大，无法上传。本处删除了除了2张关于提供曲线和需求曲张关于提供曲线和需求曲线的几何图形的图片格式，请看线的几何图形的图片格式，请看教材图形。教材图形。cymSome Results about Price ChangeuIf a consumer is a net seller of a good,when the price of the good decreases,if she

11、remains a buyer then the consumer is worse off.uIf a consumer if a net buyer of a good,when the price decreases,the consumer will remain a buyer and be better off.因课件太大，无法上传。本处删除了因课件太大，无法上传。本处删除了2张关于价格变动（商品张关于价格变动（商品1价格下降、上价格下降、上升）的几何图形的图片格式，请看教升）的几何图形的图片格式，请看教材图形。材图形。cymLabor SupplyuA worker is end

12、owed with$m of nonlabor income and R hours of time which can be used for labor or leisure.w w=(R,m).uConsumption goods price is pc.uw is the wage rate.Labor SupplyuThe workers budget constraint iswhere C,R denote gross demands for the consumption good and for leisure.That isendowment valueexpenditur

13、eLabor Supplyrearranges toLabor SupplyCRRendowmentm($)Labor SupplyCRRendowmentmLabor SupplyCRRendowmentmLabor SupplyCRRendowmentmslope=,the real wage rateLabor SupplyCRRendowmentmC*R*leisuredemanded laborsuppliedLabor Supply CurveSlutskys Equation RevisiteduSlutsky:changes to demands caused by a pri

14、ce change are the sum ofa pure substitution effect,andan income effect.uThis assumed that income y did not change as prices changed.But does change with price.How does this modify Slutskys equation?Slutskys Equation RevisiteduA change in p1 or p2 changes so there will bean additional income effect,c

15、alled the endowment income effect（禀赋收入效应）禀赋收入效应）.uSlutskys decomposition will thus have three componentsa pure substitution effectan(ordinary)income effect,andan endowment income effect.Slutskys Equation Revisitedx1w w2w w1x2x2x1Initial prices are(p1,p2).Slutskys Equation Revisitedx1w w2w w1x2x2x1”x

16、2”Initial prices are(p1,p2).Final prices are(p1”,p2”).x1Slutskys Equation Revisitedx1w w2w w1x2x2x1”x2”Initial prices are(p1,p2).Final prices are(p1”,p2”).How is the change in demandfrom(x1,x2)to(x1”,x2”)explained?x1Slutskys Equation Revisitedx1w w2w w1x2x2x1Initial prices are(p1,p2).Slutskys Equati

17、on Revisitedx1w w2w w1x2x2x1”x2”Initial prices are(p1,p2).Final prices are(p1”,p2”).x1Slutskys Equation Revisitedx1w w2w w1x2Pure substitution effectSlutskys Equation Revisitedx1w w2w w1x2Pure substitution effectSlutskys Equation Revisitedx1w w2w w1x2Pure substitution effectOrdinary income effectSlu

18、tskys Equation Revisitedx1w w2w w1x2Pure substitution effectOrdinary income effectSlutskys Equation Revisitedx1w w2w w1x2Pure substitution effectOrdinary income effectEndowment income effectSlutskys Equation Revisitedx1w w2w w1x2Pure substitution effectOrdinary income effectEndowment income effectSlutskys Equation RevisitedOverall change in demand caused by achange in price is the sum of:(i)a pure substitution effect(ii)an ordinary income effect(iii)an endowment income effectSlutsky Equation with EndowmentsOr(-)(+)(+)