经济学原理 曼昆课后答案 chapter 7.docx

经济学原理 曼昆课后答案 chapter 7.docx

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经济学原理曼昆课后答案chapter7

ProblemsandApplications

1.IfanearlyfreezeinCaliforniasoursthelemoncrop,thesupplycurveforlemonsshiftstotheleft,asshowninFigure7-5.TheresultisariseinthepriceoflemonsandadeclineinconsumersurplusfromA+B+CtojustA.SoconsumersurplusdeclinesbytheamountB+C.

Figure7-5

Inthemarketforlemonade,thehighercostoflemonsreducesthesupplyoflemonade,asshowninFigure7-6.TheresultisariseinthepriceoflemonadeandadeclineinconsumersurplusfromD+E+FtojustD,alossofE+F.Notethataneventthataffectsconsumersurplusinonemarketoftenhaseffectsonconsumersurplusinothermarkets.

Figure7-6

2.AriseinthedemandforFrenchbreadleadstoanincreaseinproducersurplusinthemarketforFrenchbread,asshowninFigure7-7.Theshiftofthedemandcurveleadstoanincreasedprice,whichincreasesproducersurplusfromareaAtoareaA+B+C.

Figure7-7

TheincreasedquantityofFrenchbreadbeingsoldincreasesthedemandforflour,asshowninFigure7-8.Asaresult,thepriceofflourrises,increasingproducersurplusfromareaDtoD+E+F.Notethataneventthataffectsproducersurplusinonemarketleadstoeffectsonproducersurplusinrelatedmarkets.

Figure7-8

3.a.Bert’sdemandscheduleis:

Price

QuantityDemanded

Morethan$7

0

$5to$7

1

$3to$5

2

$1to$3

3

$1orless

4

Bert’sdemandcurveisshowninFigure7-9.

Figure7-9

b.Whenthepriceofabottleofwateris$4,Bertbuystwobottlesofwater.HisconsumersurplusisshownasareaAinthefigure.Hevalueshisfirstbottleofwaterat$7,butpaysonly$4forit,sohasconsumersurplusof$3.Hevalueshissecondbottleofwaterat$5,butpaysonly$4forit,sohasconsumersurplusof$1.ThusBert’stotalconsumersurplusis$3+$1=$4,whichistheareaofAinthefigure.

c.Whenthepriceofabottleofwaterfallsfrom$4to$2,Bertbuysthreebottlesofwater,anincreaseofone.HisconsumersurplusconsistsofbothareasAandBinthefigure,anincreaseintheamountofareaB.Hegetsconsumersurplusof$5fromthefirstbottle（$7valueminus$2price）,$3fromthesecondbottle（$5valueminus$2price）,and$1fromthethirdbottle（$3valueminus$2price）,foratotalconsumersurplusof$9.Thusconsumersurplusrisesby$5（whichisthesizeofareaB）whenthepriceofabottleofwaterfallsfrom$4to$2.

4.a.Ernie’ssupplyscheduleforwateris:

Price

QuantitySupplied

Morethan$7

4

$5to$7

3

$3to$5

2

$1to$3

1

Lessthan$1

0

Ernie’ssupplycurveisshowninFigure7-10.

Figure7-10

b.Whenthepriceofabottleofwateris$4,Erniesellstwobottlesofwater.HisproducersurplusisshownasareaAinthefigure.Hereceives$4forhisfirstbottleofwater,butitcostsonly$1toproduce,soErniehasproducersurplusof$3.Healsoreceives$4forhissecondbottleofwater,whichcosts$3toproduce,sohehasproducersurplusof$1.ThusErnie’stotalproducersurplusis$3+$1=$4,whichistheareaofAinthefigure.

c.Whenthepriceofabottleofwaterrisesfrom$4to$6,Erniesellsthreebottlesofwater,anincreaseofone.HisproducersurplusconsistsofbothareasAandBinthefigure,anincreasebytheamountofareaB.Hegetsproducersurplusof$5fromthefirstbottle（$6priceminus$1cost）,$3fromthesecondbottle（$6priceminus$3cost）,and$1fromthethirdbottle（$6priceminus$5price）,foratotalproducersurplusof$9.Thusproducersurplusrisesby$5（whichisthesizeofareaB）whenthepriceofabottleofwaterrisesfrom$4to$6.

5.a.FromErnie’ssupplyscheduleandBert’sdemandschedule,thequantitydemandedandsuppliedare:

Price

QuantitySupplied

QuantityDemanded

$2

1

3

4

2

2

6

3

1

Onlyapriceof$4bringssupplyanddemandintoequilibrium,withanequilibriumquantityof2.

b.Atapriceof$4,consumersurplusis$4andproducersurplusis$4,asshowninproblems3and4.Totalsurplusis$4+$4=$8.

c.IfErnieproducedonefewerbottle,hisproducersurpluswoulddeclineto$3,asshowninproblem4.IfBertconsumedonefewerbottle,hisconsumersurpluswoulddeclineto$3,asshowninproblem3.Sototalsurpluswoulddeclineto$3+$3=$6.

d.IfErnieproducedoneadditionalbottleofwater,hiscostwouldbe$5,butthepriceisonly$4,sohisproducersurpluswoulddeclineby$1.IfBertconsumedoneadditionalbottleofwater,hisvaluewouldbe$3,butthepriceis$4,sohisconsumersurpluswoulddeclineby$1.Sototalsurplusdeclinesby$1+$1=$2.

6.a.Theeffectoffallingproductioncostsinthemarketforstereosresultsinashifttotherightinthesupplycurve,asshowninFigure7-11.Asaresult,theequilibriumpriceofstereosdeclinesandtheequilibriumquantityincreases.

b.ThedeclineinthepriceofstereosincreasesconsumersurplusfromareaAtoA+B+C+D,anincreaseintheamountB+C+D.Priortotheshiftinsupply,producersurpluswasareasB+E（theareaabovethesupplycurveandbelowtheprice）.Aftertheshiftinsupply,producersurplusisareasE+F+G.SoproducersurpluschangesbytheamountF+G-B,whichmaybepositiveornegative.Theincreaseinquantityincreasesproducersurplus,whilethedeclineinthepricereducesproducersurplus.SinceconsumersurplusrisesbyB+C+DandproducersurplusrisesbyF+G-B,totalsurplusrisesbyC+D+F+G.

c.Ifthesupplyofstereosisveryelastic,thentheshiftofthesupplycurvebenefitsconsumersmost.Totakethemostdramaticcase,supposethesupplycurvewerehorizontal,asshowninFigure7-12.Thenthereisnoproducersurplusatall.Consumerscaptureallthebenefitsoffallingproductioncosts,withconsumersurplusrisingfromareaAtoareaA+B.

Figure7-11

Figure7-12

7.Figure7-13showssupplyanddemandcurvesforhaircuts.Supplyequalsdemandataquantityofthreehaircutsandapricebetween$4and$5.FirmsA,C,andDshouldcutthehairofSallyJessy,Jerry,andMontel.Oprah’swillingnesstopayistoolowandfirmB’scostsaretoohigh,sotheydonotparticipate.Themaximumtotalsurplusistheareabetweenthedemandandsupplycurves,whichtotals$11（$8valueminus$2costforthefirsthaircut,plus$7valueminus$3costforthesecond,plus$5valueminus$4costforthethird）.

Figure7-13

8.a.Theeffectoffallingproductioncostsinthemarketforcomputersresultsinashifttotherightinthesupplycurve,asshowninFigure7-14.Asaresult,theequilibriumpriceofcomputersdeclinesandtheequilibriumquantityincreases.ThedeclineinthepriceofcomputersincreasesconsumersurplusfromareaAtoA+B+C+D,anincreaseintheamountB+C+D.

Figure7-14

Priortotheshiftinsupply,producersurpluswasareasB+E（theareaabovethesupplycurveandbelowtheprice）.Aftertheshiftinsupply,producersurplusisareasE+F+G.SoproducersurpluschangesbytheamountF+G-B,whichmaybepositiveornegative.Theincreaseinquantityincreasesproducersurplus,whilethedeclineinthepricereducesproducersurplus.SinceconsumersurplusrisesbyB+C+DandproducersurplusrisesbyF+G-B,totalsurplusrisesbyC+D+F+G.

Figure7-15

b.Sinceaddingmachinesaresubstitutesforcomputers,thedeclineinthepriceofcomputersmeansthatpeoplesubstitutecomputersforaddingmachines,shiftingthedemandforaddingmachinestotheleft,asshowninFigure7-15.Theresultisadeclineinboththeequilibriumpriceandequilibriumquantityofaddingmachines.Consumersurplusintheadding-machinemarketchangesfromareaA+BtoA+C,anetgainofC-B.ProducersurpluschangesfromareaC+D+EtoareaE,anetlossofC+D.Addingmachineproducersaresadabouttechnologicaladvanceincomputersbecausetheirproducersurplusdeclines.

c.Sincesoftwareandcomputersarecomplements,thedeclineinthepriceandincreaseinthequantityofcomputersmeansthatpeople’sdemandforsoftwareincreases,shiftingthedemandforsoftwaretotheright,asshowninFigure7-16.Theresultisanincreaseinboththepriceandquantityofsoftware.ConsumersurplusinthesoftwaremarketchangesfromB+CtoA+B,anetincreaseofA-C.ProducersurpluschangesfromEtoC+D+E,anincreaseofC+D,sosoftwareproducersshouldbehappyaboutthetechnologicalprogressincomputers.

d.Yes,thisanalysishelpsexplainwhyBillGatesisonetheworld’srichestmen,sincehiscompanyproducesalotofsoftwarethat’sacomplementwithcomputersandtherehasbeentremendoustechnologicaladvanceincomputers.

Figure7-16

9.a.Figure7-17illustratesthedemandformedicalcare.Ifeachprocedurehasapriceof$100,quantitydemandedwillbeQ1procedures.

Figure7-17

b.Ifconsumerspayonly$20perprocedure,thequantitydemandedwillbeQ2procedures.Sincethecosttosocietyis$100,thenumberofproceduresperformedistoolargetomaximizetotalsurplus.ThequantitythatmaximizestotalsurplusisQ1procedures,whichislessthanQ2.

c.Theuseofmedicalcareisexcessiveinthesensethatconsumersgetprocedureswhosevalueislessthanthecostofproducingthem.Asaresult,theeconomy’stotalsurplusisreduced.

d.Topreventthisexcessiveuse,theconsumermustbearthemarginalcostoftheprocedure.Butthiswouldrequireeliminatinginsurance.Anotherpossibilitywouldbethattheinsurancecompany,whichpaysmostofthemarginalcostoftheprocedure（$80,inthiscase）coulddecidewhethertheprocedureshouldbeperformed.Buttheinsurancecompanydoesn’tgetthebenefitsoftheprocedure,soitsdecisionsmaynotreflectthevaluetothec