中级微观经济学 第六讲.pdf

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1、北京大学国家发展研究院2014年秋季学期本科双学位课程中级微观经济学(2班)第六讲：购买和销售任课教师：李力行第9章购买和销售Endowments（禀赋）BudgetconstraintswithendowmentsNetdemands-PriceoffercurveExample:Laborsupply-ComparativestaticsSlutskyequationrevisitedBuyingandSellingHowisincomegenerated?Whensomethingisboughtsomethingelsemustbesold.Whatwil

2、lbebought?Whatwillbesold?Whowillbeabuyer?Whowillbeaseller?Howdoesthevalueofincomedependuponcommodityprices?EndowmentsThelistofresourcewithwhichaconsumerstartsishisendowment.Aconsumer’sendowmentwillbedenotedbythevector.E.g.(1,2)(10,2)statesthattheconsumerisendowedwith10unitsofgood1an

3、d2unitsofgood2.Whatistheendowment’svalue?Forwhichconsumptionbundlesmayitbeexchanged?Endowmentsp=2andp=3sothevalueofthe12endowmentis(1,2)(10,2)p11p222103226Q:Forwhichconsumptionbundlesmaytheendowmentbeexchanged?A:Foranybundlecostingnomorethantheendowment’svalue.BudgetConstraint

4、sRevisitedSo,givenpandp,thebudget12constraintforaconsumerwithanendowmentis(1,2)p1x1p2x2p11p22.Thebudgetsetis(x1,x2)p1x1p2x2p11p22,x10,x20.BudgetConstraintsRevisitedx2p1x1p2x2p11p222Budgetset(x1,x2)p1x1p2x2p11p22,x10,x201x1BudgetConstraintsRevisitedx2p1x1p2x2

5、p11p222Budgetset''''p1x1p2x2p11p221x1BudgetConstraintsRevisitedTheendowmentpointisalwaysonx2thebudgetconstraint.p1x1p2x2p11p22Sopricechangespivottheconstraintaroundthe2endowmentpoint.''''p1x1p2x2p11p221x1BudgetConstraintsRevisitedTheconstraintpxpxpp11221122isp1(x1

6、1)p2(x22)0.Thatis,thesumofthevaluesofaconsumer’snetdemandiszero.NetDemandsSupposeand(1,2)(10,2)p=2,p=3.Thentheconstraintis12p1x1p2x2p11p2226.Iftheconsumerdemands(x*,x*)=12(7,4),then3unitsofgood1exchangefor2unitsofgood2.Netdemandsarex*-=7-10=-3and11x*-=4-2=+2.22NetDemandsp=

7、2,p=3,x*-=-3andx*-=+2so121122p1(x11)p2(x22)2(3)320.Thepurchaseof2extraunitsofgood2at$3eachisfundedbygivingup3unitsofgood1at$2each.NetDemandsp1(x11)p2(x22)0x2Atprices(p,p)theconsumer12x*sellsunitsofgood1toacquire2moreunitsof