微观经济学（第八版-英文）课件：The Analysis of Competitive Markets

9.1

EvaluatingtheGainsandLossesfromGovernmentPolicies—ConsumerandProducerSurplus9.2

TheEfficiencyofCompetitiveMarkets9.3

MinimumPrices9.4

PriceSupportsandProductionQuotas9.5

ImportQuotasandTariffs9.6

TheImpactofaTaxorSubsidy

TheAnalysisofCompetitiveMarketsCHAPTEROUTLINEEvaluatingtheGainsandLosses

fromGovernmentPolicies—

ConsumerandProducerSurplus9.1Inthischapter,wereturntosupply–demandanalysisandshowhowitcanbeappliedtoawidevarietyofeconomicproblems—problemsthatmightconcernaconsumerfacedwithapurchasingdecision,afirmfacedwithalong-rangeplanningproblem,oragovernmentagencythathastodesignapolicyandevaluateitslikelyimpact.Webeginbyshowinghowconsumerandproducersurpluscanbeusedtostudythewelfareeffectsofagovernmentpolicy—inotherwords,whogainsandwholosesfromthepolicy,andbyhowmuch.Wealsouseconsumerandproducersurplustodemonstratetheefficiencyofacompetitivemarket.Youwillseehowtocalculatetheresponseofmarketstochangingeconomicconditionsorgovernmentpoliciesandtoevaluatetheresultinggainsandlossestoconsumersandproducers.ReviewofConsumerandProducerSurplusConsumerAwouldpay$10foragoodwhosemarketpriceis$5andthereforeenjoysabenefitof$5.ConsumerBenjoysabenefitof$2,andConsumerC,whovaluesthegoodatexactlythemarketprice,enjoysnobenefit.Consumersurplus,whichmeasuresthetotalbenefittoallconsumers,istheyellow-shadedareabetweenthedemandcurveandthemarketprice.CONSUMERANDPRODUCERSURPLUSFIGURE9.1(1OF2)CONSUMERANDPRODUCERSURPLUSFIGURE9.1(2of2)Producersurplusmeasuresthetotalprofitsofproducers,plusrentstofactorinputs.Itisthebenefitthatlower-costproducersenjoybysellingatthemarketprice,shownbythegreen-shadedareabetweenthesupplycurveandthemarketprice.Together,consumerandproducersurplusmeasurethewelfarebenefitofacompetitivemarket.ApplicationofConsumerandProducerSurplusCHANGEINCONSUMERANDPRODUCERSURPLUSFROMPRICECONTROLSFIGURE9.2●

welfareeffects Gainsandlossestoconsumersandproducers.ThepriceofagoodhasbeenregulatedtobenohigherthanPmax,whichisbelowthemarket-clearingpriceP0.ThegaintoconsumersisthedifferencebetweenrectangleAandtriangleB.ThelosstoproducersisthesumofrectangleAandtriangleC.TrianglesBandCtogethermeasurethedeadweightlossfrompricecontrols.●

deadweightloss Netlossoftotal(consumerplusproducer)surplus.ApplicationofConsumerandProducerSurplusEFFECTOFPRICECONTROLSWHENDEMANDISINELASTICFIGURE9.3Ifdemandissufficientlyinelastic,triangleBcanbelargerthanrectangleA.Inthiscase,consumerssufferanetlossfrompricecontrols.EFFECTSOFNATURALGASPRICECONTROLSFIGURE9.4EXAMPLE9.1PRICECONTROLSANDNATURALGASSHORTAGESSupply:QS=15.90+0.72PG+0.05PODemand:QD=0.02−1.8PG

+0.69POThemarket-clearingpriceofnaturalgaswas$6.40permcf,andthe(hypothetical)maximumallowablepriceis$3.00.Ashortageof29.1−20.6=8.5Tcfresults.ThegaintoconsumersisrectangleAminustriangleB,andthelosstoproducersisrectangleAplustriangleC.ThedeadweightlossisthesumoftrianglesBplusC.EFFECTSOFNATURALGASPRICECONTROLSFIGURE9.4(supplement)EXAMPLE9.1PRICECONTROLSANDNATURALGASSHORTAGESA=(20.6billionmcf)

($3.40/mcf)=$70.04billionB=(1/2)x(2.4billionmcf)

($1.33/mcf)=$1.60billionC=(1/2)x(2.4billionmcf)

($3.40/mcf)=$4.08billionTheannualchangeinconsumersurplusthatwouldresultfromthesehypotheticalpricecontrolswouldthereforebeA−

B=70.04−1.60=$68.44billion.Thechangeinproducersurpluswouldbe−A−C=−70.04−4.08=−$74.12billion.Andfinally,theannualdeadweightloss.wouldbe−B−C=−1.60−4.08=−$5.68billion.TheEfficiencyofaCompetitiveMarket9.2MARKETFAILURE●economicefficiency Maximizationofaggregateconsumerandproducersurplus.●marketfailure Situationinwhichanunregulatedcompetitivemarketisinefficientbecausepricesfailtoprovidepropersignalstoconsumersandproducers.●

externalityActiontakenbyeitheraproduceroraconsumerwhichaffectsotherproducersorconsumersbutisnotaccountedforbythemarketprice.Therearetwoimportantinstancesinwhichmarketfailurecanoccur:ExternalitiesLackofInformationMarketfailurecanalsooccurwhenconsumerslackinformationaboutthequalityornatureofaproductandsocannotmakeutility-maximizingpurchasingdecisions.Governmentintervention(e.g.,requiring“truthinlabeling”)maythenbedesirable.ReviewofConsumerandProducerSurplusWELFARELOSSWHENPRICEISHELDABOVEMARKET-CLEARINGLEVELFIGURE9.5WhenpriceisregulatedtobenolowerthanP2,onlyQ3willbedemanded.IfQ3isproduced,thedeadweightlossisgivenbytrianglesBandC.AtpriceP2,producerswouldliketoproducemorethanQ3.Iftheydo,thedeadweightlosswillbeevenlarger.EXAMPLE8.2THEMARKETFORHUMANKIDNEYSEvenatapriceofzero(theeffectivepriceunderthelaw),donorssupplyabout16,000kidneysperyear.Ithasbeenestimatedthat8000morekidneyswouldbesuppliedifthepricewere$20,000.Wecanfitalinearsupplycurvetothisdata—i.e.,asupplycurveoftheformQ=a+bP.WhenP=0,Q=16,000,soa=16,000.IfP=$20,000,Q=24,000,sob=(24,000

16,000)/20,000=0.4.ThusthesupplycurveisSupply:QS

=16,000+0.4PNotethatatapriceof$20,000,theelasticityofsupplyis0.33.Itisexpectedthatatapriceof$20,000,thenumberofkidneysdemandedwouldbe24,000peryear.Likesupply,demandisrelativelypriceinelastic;areasonableestimateforthepriceelasticityofdemandatthe$20,000priceis−0.33.Thisimpliesthefollowinglineardemandcurve:Demand:QD

=32,000

0.4PTHEMARKETFORKIDNEYSANDTHEEFFECTOFTHENATIONALORGANTRANSPLANTATIONACTFIGURE9.6EXAMPLE8.2THEMARKETFORHUMANKIDNEYSEconomics,thedismalscience,showsusthathumanorganshaveeconomicvaluethatcannotbeignored,andprohibitingtheirsaleimposesacostonsocietythatmustbeweighedagainstthebenefits.Themarket-clearingpriceis$20,000;atthisprice,about24,000kidneysperyearwouldbesupplied.Thelaweffectivelymakesthepricezero.About16,000kidneysperyeararestilldonated;thisconstrainedsupplyisshownasS’.ThelosstosuppliersisgivenbyrectangleAandtriangleC.Ifconsumersreceivedkidneysatnocost,theirgainwouldbegivenbyrectangleAlesstriangleB.PRICEMINIMUMFIGURE9.7MinimumPrices9.3Thetotalchangeinconsumersurplusis:

CS=−A−

BThetotalchangeinproducersurplusis:

PS=A−

C−

DPriceisregulatedtobenolowerthanPmin.ProducerswouldliketosupplyQ2,butconsumerswillbuyonlyQ3.IfproducersindeedproduceQ2,theamountQ2−Q3willgounsoldandthechangeinproducersurpluswillbeA−C−D.Inthiscase,producersasagroupmaybeworseoff.THEMINIMUMWAGEFIGURE9.8Althoughthemarket-clearingwageisw0,firmsarenotallowedtopaylessthanwmin.ThisresultsinunemploymentofanamountL2−L1andadeadweightlossgivenbytrianglesBandC.EFFECTOFAIRLINEREGULATIONBYTHECIVILAERONAUTICSBOARDFIGURE9.9EXAMPLE8.2AIRLINEREGULATIONAirlinederegulationin1981ledtomajorchangesintheindustry.Someairlinesmergedorwentoutofbusinessasnewonesentered.Althoughpricesfellconsiderably(tothebenefitofconsumers),profitsoveralldidnotfallmuch.AtpricePmin,airlineswouldliketosupplyQ2,wellabovethequantityQ1thatconsumerswillbuy.HeretheysupplyQ3.TrapezoidDisthecostofunsoldoutput.AirlineprofitsmayhavebeenlowerasaresultofregulationbecausetriangleCandtrapezoidDcantogetherexceedrectangleA.Inaddition,consumersloseA+B.EXAMPLE8.2AIRLINEREGULATIONBecauseairlineshavenocontroloveroilprices,itismoreinformativetoexaminea“corrected”realcostindexwhichremovestheeffectsofchangingfuelcosts.TABLE9.1AIRLINEINDUSTRYDATA19751980199020002010NumberofU.S.carriers3663709463PassengerLoadFactor(%)54.058.062.472.182.1Passenger-MileRate(constant1995dollars)0.2180.2100.1490.1180.094RealCostIndex(1995=100)10114511989148RealFuelCostIndex(1995=100)249300163125342RealCostIndexw/oFuelCostIncreases(1995=100)71871048576PriceSupportsandProductionQuotas9.4PriceSupports●pricesupport Pricesetbygovernmentabovefree-marketlevelandmaintainedbygovernmentalpurchasesofexcesssupply.PRICESUPPORTSFIGURE9.10TomaintainapricePsabovethemarket-clearingpriceP0,thegovernmentbuysaquantityQg.ThegaintoproducersisA+B+D.ThelosstoconsumersisA+B.Thecosttothegovernmentisthespeckledrectangle,theareaofwhichisPs(Q2−Q1).CONSUMERSLet’sexaminetheresultinggainsandlossestoconsumers,producers,andthegovernmentinFigure9.10.Someconsumerspayahigherprice,whileothersnolongerbuythegood.

PRODUCERSProducersarenowsellingalargerquantityQ2insteadofQ0,andatahigherpricePs.

THEGOVERNMENTThecosttothegovernment(whichisultimatelyacosttoconsumers)is

Thetotalchangeinwelfareis

ProductionQuotasSUPPLYRESTRICTIONSFIGURE9.11TomaintainapricePsabovethemarket-clearingpriceP0,thegovernmentcanrestrictsupplytoQ1,eitherbyimposingproductionquotas(aswithtaxicabmedallions)orbygivingproducersafinancialincentivetoreduceoutput(aswithacreagelimitationsinagriculture).Foranincentivetowork,itmustbeatleastaslargeasB+C+D,whichwouldbetheadditionalprofitearnedbyplanting,giventhehigherpricePs.ThecosttothegovernmentisthereforeatleastB+C+D.Q1INCENTIVEPROGRAMSInU.S.agriculturalpolicy,outputisreducedbyincentivesratherthanbyoutrightquotas.Acreagelimitationprogramsgivefarmersfinancialincentivestoleavesomeoftheiracreageidle.Figure9.11alsoshowsthewelfareeffectsofreducingsupplyinthisway.Aswithdirectproductionquotas,thechangeinconsumersurplusis

Farmersreceiveahigherprice,produceless,andreceiveanincentivetoreduceproduction.Thus,thechangeinproducersurplusisnow

ThecosttothegovernmentisatleastB+C+D,andthetotalchangeinproducersurplusis

Anacreage-limitationprogramismorecostlytosocietythansimplyhandingthefarmersmoney.Thetotalchangeinwelfare

THEWHEATMARKET

IN1981FIGURE9.12EXAMPLE9.4SUPPORTINGTHEPRICEOFWHEAT1981Supply:QS=1800+240P1981Demand:QD=3550266PToincreasethepriceto$3.70,thegovernmentmustbuyaquantityofwheatQg.Bybuying122millionbushelsofwheat,thegovernmentincreasedthemarket-clearingpricefrom$3.46perbushelto$3.70.1981Totaldemand:QD=3550266P+QgQg=506P

1750Qg=(506)(3.70)

1750=112millionbushelsLosstoconsumers=−A−B=$624millionCosttothegovernment=$3.70

112million=$451.4millionTotalcostoftheprogram=$624million+$451.4million=$1075millionGaintoproducers=A+B+C=$638millionEXAMPLE9.4SUPPORTINGTHEPRICEOFWHEATIn1996,theU.S.Congresspassedanewfarmbill,nicknamedthe“FreedomtoFarm”law.Thelaweliminatedproductionquotas(forwheat,corn,rice,andotherproducts)andgraduallyreducedgovernmentpurchasesandsubsidiesthrough2003.InExample2.5,wesawthatthemarket-clearingpriceofwheatin2007hadincreasedtoabout$6.00perbushel.Thesupplyanddemandcurvesin2007wereasfollows:Supply:QS=2900+125PDemand:QD=1460

115PYoucanchecktoseethatthemarket-clearingquantityis2150millionbushels.in2002,theFarmSecurityandRuralInvestmentActreinstatedsubsidiesformostcrops,inparticulargrainandcotton.Itcalledforthegovernmenttoissue“fixeddirectpayments”toproducers.Congressrevisitedagriculturalsubsidiesin2007,andthesubsidieswereeithermaintainedorincreased,thusmakingtheburdenonU.S.taxpayersevenhigher.Recently,however,thependulumhasswungbacktowardeliminatingsubsidies,andnewcutswereapprovedaspartofthedealtoresolvethe2011budgetcrisis.EXAMPLE9.5WHYCAN’TIFINDATAXI?ThecityofNewYorklimitsthenumberoftaxisbyrequiringeachtaxitohaveamedallion(essentiallyapermit),andthenlimitingthenumberofmedallions.In2011therewere13,150medallionsinNewYork—roughlythesamenumberasin1937.Whynotjustissuemoremedallions?Thereasonissimple.Doingsowouldincurthewrathofthecurrentownersofmedallions.Medallionscanbeboughtandsoldbythecompaniesthatownthem.In1937,therewereplentyofmedallionstogoaround,sotheyhadlittlevalue.By1947,thevalueofamedallionhadincreasedto$2,500,by1980to$55,000,andby2011to$880,000.That’sright—becauseNewYorkCitywon’tissuemoremedallions,thevalueofataximedallionisapproaching$1million!Butofcoursethatvaluewoulddropsharplyifthecitystartingissuingmoremedallions.SotheNewYorktaxicompaniesthatcollectivelyownthe13,150availablemedallionshavedoneeverythingpossibletopreventthecityfromissuinganymore—andhavesucceededintheirefforts.Ifthecityweretoissueanother7,000medallionsforatotalofabout20,000,demandandsupplywouldequilibrateatapriceofabout$350,000permedallion–stillalot,butjustenoughtoleasecabs,runataxibusiness,andstillmakeaprofit.EXAMPLE9.5WHYCAN’TIFINDATAXI?TAXIMEDALLIONSINNEWYORKCITYFIGURE9.13ThedemandcurveDshowsthequantityofmedallionsdemandedbytaxicompaniesasafunctionofthepriceofamedallion.ThesupplycurveSshowsthenumberofmedallionsthatwouldbesoldbycurrentownersasafunctionofprice.NewYorklimitsthequantityto13,150,sothesupplycurvebecomesverticalandintersectsdemandat$880,000,themarketpriceofamedallionin2011.ImportQuotasandTariffs9.5●importquota Limitonthequantityofagoodthatcanbeimported.IMPORTTARIFFORQUOTATHATELIMINATESIMPORTSFIGURE9.14●tariff Taxonanimportedgood.Inafreemarket,thedomesticpriceequalstheworldpricePw.AtotalQdisconsumed,ofwhichQsissupplieddomesticallyandtherestimported.Whenimportsareeliminated,thepriceisincreasedtoP0.ThegaintoproducersistrapezoidA.ThelosstoconsumersisA+B+C,sothedeadweightlossisB+C.IMPORTTARIFFORQUOTA(GENERALCASE)FIGURE9.15Whenimportsarereduced,thedomesticpriceisincreasedfromPwtoP*.Thiscanbeachievedbyaquota,orbyatariffT=P*−Pw.TrapezoidAisagainthegaintodomesticproducers.ThelosstoconsumersisA+B+C+D.Ifatariffisused,thegovernmentgainsD,therevenuefromthetariff.ThenetdomesticlossisB+C.Ifaquotaisusedinstead,rectangleDbecomespartoftheprofitsofforeignproducers,andthenetdomesticlossisB+C+D.EXAMPLE9.6THESUGARQUOTAInrecentyears,theworldpriceofsugarhasbeenbetween10and28centsperpound,whiletheU.S.pricehasbeen30to40centsperpound.Why?Byrestrictingimports,theU.S.governmentprotectsthe$4billiondomesticsugarindustry,whichwouldvirtuallybeputoutofbusinessifithadtocompetewithlow-costforeignproducers.ThispolicyhasbeengoodforU.S.sugarproducers,butbadforconsumers.U.S.production:15.9billionpoundsU.S.consumption:22.8billionpoundsU.S.price:36centsperpoundWorldprice24centsperpoundU.S.supply:QS=

7.95

+0.66PU.S.demand:QD=29.730.19PAtthe24-centworldprice,U.S.productionwouldhavebeenonlyabout7.9billionpoundsandU.S.consumptionabout25.2billionpounds,ofwhich25.2−7.9=17.3billionpoundswouldhavebeenimported.ButfortunatelyforU.S.producers,importswerelimitedtoonly6.9billionpounds.EXAMPLE9.6THESUGARQUOTASUGARQUOTAIN2010FIGURE9.16Attheworldpriceof24centsperpound,about25.2billionpoundsofsugarwouldhavebeenconsumedofwhichallbut7.9billionpoundswouldhavebeenimported.Restrictingimportsto6.9billionpoundscausedtheU.S.pricetogoupby12cents.Thecosttoconsumers,A+B+C+D,wasabout$2.9billion.ThegaintodomesticproducerswastrapezoidA,about$1.4billion.RectangleD,$836million,wasagaintothoseforeignproducerswhoobtainedquotaallotments.TrianglesBandCrepresentthedeadweightlossofabout$614million.TheImpactofaTaxorSubsidy9.6INCIDENCEOFATAXFIGURE9.17●

specifictaxTaxofacertainamountofmoneyperunitsold.Pbistheprice(includingthetax)paidbybuyers.Psisthepricethatsellersreceive,lessthetax.Heretheburdenofthetaxissplitevenlybetweenbuyersandsellers.BuyersloseA+B.SellersloseD+C.ThegovernmentearnsA+Dinrevenue.ThedeadweightlossisB+C.Marketclearingrequiresfourconditions