lecture03市场福利分析

LecturethreeMarketandWelfare©2007ThomsonSouth-Western消费者、生产者与市场效率Consumers,ProducersandtheEfficiencyofMarketsRevisitingtheMarketEquilibriumDotheequilibriumpriceandquantitymaximizethetotalwelfareofbuyersandsellers?Marketequilibriumreflectsthewaymarketsallocatescarceresources.Whetherthemarketallocationisdesirablecanbeaddressedbywelfareeconomics.消费者、生产者与市场效率回顾市场均衡

市场均衡价格和数量能否使买者和卖者的总利益最大化？市场均衡反映了市场配置稀缺资源的方式。市场配置资源是否合意可以根据福利经济学理论判定。Consumers,ProducersandtheEfficiencyofMarkets

WelfareEconomicsWelfareeconomicsisthestudyofhowtheallocationof

resourcesaffectseconomicwell-being.Buyersandsellersreceivebenefitsfromtakingpartinthemarket.Theequilibriuminamarketmaximizesthetotalwelfareofbuyersandsellers.消费者、生产者与市场效率福利经济学福利经济学研究资源配置如何影响经济福利。买者和卖者可以从参与市场活动中获得利益。市场均衡可以使买者和卖者的总利益最大化。Consumers,ProducersandtheEfficiencyofMarkets

WelfareEconomicsEquilibriuminthemarketresultsinmaximumbenefits,andthereforemaximumtotalwelfareforboththeconsumersandtheproducersoftheproduct.消费者、生产者与市场效率福利经济学市场均衡使利益最大化，即使产品的消费者和生产者的总利益最大化。Consumers,ProducersandtheEfficiencyofMarkets

WelfareEconomicsConsumersurplusmeasureseconomicwelfarefromthebuyer’sside.Producersurplusmeasureseconomicwelfarefromtheseller’s

side.消费者、生产者与市场效率福利经济学消费者剩余从消费者角度衡量经济福利。生产者剩余从生产者角度衡量经济福利。CONSUMERSURPLUSWillingnesstopayisthemaximumamountthatabuyerwillpayforagood.Itmeasureshowmuchthebuyervaluesthegoodorservice.Consumersurplus

isthebuyer’swillingnesstopayforagoodminustheamountthebuyeractuallypaysforit.消费者剩余支付意愿——买者为某种物品愿意和能够支付的最高价格。它衡量买者对物品的评价是多少。消费者剩余——买者支付意愿减去买者的实际支付量。Table1:FourPossibleBuyers’WillingnesstoPay表1.四个可能买者的支付意愿买者支付意愿约翰100美元保罗80乔治70林格50UsingtheDemandCurvetoMeasureConsumerSurplusThemarketdemandcurvedepictsthevariousquantitiesthatbuyerswouldbewillingandabletopurchaseatdifferentprices.用需求曲线衡量消费者剩余市场需求曲线表示在不同价格水平下买者愿意和能够购买的数量。TheDemandScheduleandtheDemandCurve需求表与需求曲线Figure1TheDemandScheduleandtheDemandCurvePriceofAlbum0QuantityofAlbumsDemand1234$100John’swillingnesstopay80Paul’swillingnesstopay70George’swillingnesstopay50Ringo’swillingnesstopay图1.需求表与需求曲线专辑的价格5070800$1001234专辑的数量约翰的支付意愿保罗的支付意愿乔治的支付意愿林格的支付意愿需求Figure2MeasuringConsumerSurpluswiththeDemandCurve(a)Price=$80PriceofAlbum5070800$100Demand1234QuantityofAlbumsJohn’sconsumersurplus($20)表2.用需求曲线衡量消费者剩余专辑的价格5070800$1001234专辑的数量需求约翰的消费者剩余（20美元）（a）价格=80美元Figure2MeasuringConsumerSurpluswiththeDemandCurve(b)Price=$70PriceofAlbum5070800$100Demand1234Totalconsumersurplus($40)QuantityofAlbumsJohn’sconsumersurplus($30)Paul’sconsumersurplus($10)图2.用需求曲线衡量消费者剩余(b)价格=70美元专辑的价格5070800$100

需求1234总消费者剩余(40美元)专辑的数量约翰的消费者剩余(30美元)’保罗的消费者剩余(10美元)’UsingtheDemandCurvetoMeasureConsumerSurplusTheareabelowthedemandcurveandabovethepricemeasurestheconsumersurplusinthemarket.用需求曲线衡量消费者剩余需求曲线以下和价格以上的面积衡量市场的消费者剩余。Figure3HowthePriceAffectsConsumerSurplusConsumersurplusQuantity(a)ConsumerSurplusatPricePPrice0DemandP1Q1BAC图3.价格如何影响消费者剩余消费者剩余数量(a)价格在P价格0需求P1Q1BAC时的消费者剩余Figure3HowthePriceAffectsConsumerSurplusInitialconsumersurplusQuantity(b)ConsumerSurplusatPricePPrice0DemandABCDEFP1Q1P2Q2ConsumersurplustonewconsumersAdditionalconsumersurplustoinitialconsumersQ2P2图3.价格如何影响消费者剩余数量价格0需求原来的消费者剩余原来消费者新增的消费者剩余新消费者的消费者剩余Q1P1DEFBCA（b）价格在P2时的消费者剩余WhatDoesConsumerSurplusMeasure?Consumersurplus,theamountthatbuyersarewillingtopayforagoodminustheamounttheyactuallypayforit,measuresthebenefitthatbuyersreceivefromagoodasthebuyersthemselvesperceiveit.消费者剩余衡量了什么？消费者剩余，即买者愿意为一种物品支付的量减他们实际支付的量，衡量了消费者从一种物品中得到的买者自己感觉到的利益。PRODUCERSURPLUSProducersurplus

istheamountasellerispaidforagoodminustheseller’scost.Itmeasuresthebenefittosellersparticipatinginamarket.生产者剩余生产者剩余——卖者得到的量减去卖者的成本。它衡量了卖者从参与市场中得到的利益。Table2:TheCostsofFourPossibleSellers表2.

四个可能卖者的成本买者成本玛丽900美元弗瑞达800乔治亚600格拉玛500UsingtheSupplyCurvetoMeasureProducerSurplusJustasconsumersurplusisrelatedtothedemandcurve,producersurplusiscloselyrelatedtothesupplycurve.利用供给曲线衡量生产者剩余正如消费者剩余与需求曲线密切相关一样，生产者剩余也与供给曲线紧密相关。TheSupplyScheduleandtheSupplyCurve供给表和供给曲线Figure4TheSupplyScheduleandtheSupplyCurve图4.供给表和供给曲线要油漆的房子数量油漆房子的价格500800$90006001234格拉玛的成本乔治亚的成本弗瑞达的成本

玛丽的成本供给UsingtheSupplyCurvetoMeasureProducerSurplusTheareabelowthepriceandabovethesupplycurvemeasurestheproducersurplusinamarket.利用供给曲线衡量生产者剩余价格以下和供给曲线以上的面积衡量市场的生产者剩余。Figure5MeasuringProducerSurpluswiththeSupplyCurveQuantityofHousesPaintedPriceofHousePainting500800$90006001234(a)Price=$600SupplyGrandma’sproducersurplus($100)图5.用供给曲线衡量生产者剩余要油漆的房子数量油漆房子的价格500800$90006001234供给格拉玛的生产者剩余（100美元）（a）价格=600美元Figure5MeasuringProducerSurpluswiththeSupplyCurveQuantityofHousesPaintedPriceofHousePainting500800$90006001234(b)Price=$800Georgia’sproducersurplus($200)Totalproducersurplus($500)Grandma’sproducersurplus($300)Supply图5.用供给曲线衡量生产者剩余要油漆房子的数量油漆房子的价格500800$90006001234供给格拉玛的生产者剩余（300美元）（b）价格=800美元乔治亚的生产者剩余（100美元）总生产者剩余(500美元)Figure6HowthePriceAffectsProducerSurplusProducersurplusQuantity(a)ProducerSurplusatPriceP

Price0SupplyBACQ1P1图6.价格如何影响生产者剩余生产者剩余数量(a)价格在P

价格0供给BACQ1P1时的生产者剩余Figure6HowthePriceAffectsProducerSurplusQuantity(b)ProducerSurplusatPriceP

Price0P1BCSupplyAInitialproducersurplusQ1P2Q2ProducersurplustonewproducersAdditionalproducersurplustoinitialproducersDEF图6.价格如何影响生产者剩余数量(b)价格在P

价格0P1BC供给A原来的生产者剩余Q1P2Q2新生产者的生产者剩余原来生产者新增的生产者剩余DEF时的生产者剩余MARKETEFFICIENCYConsumersurplusandproducersurplusmaybeusedtoaddressthefollowingquestion:Istheallocationofresourcesdeterminedbyfreemarketsinanywaydesirable?市场效率消费者剩余和生产者剩余可以用来回答下面问题：由自由市场决定的资源配置是以一种合意的方式进行的吗？TheBenevolentSocialPlannerConsumerSurplus=Valuetobuyers–AmountpaidbybuyersandProducerSurplus=Amountreceivedbysellers–Costtosellers仁慈的社会计划者消费者剩余=买者的评价–买者的支付量和生产者剩余=卖者得到的量–卖者的成本TheBenevolentSocialPlannerTotalsurplus=Consumersurplus+ProducersurplusorTotalsurplus=Valuetobuyers–Costtosellers仁慈的社会计划者总剩余=消费者剩余+生产者剩余或总剩余=买者的评价–卖者的成本TheBenevolentSocialPlannerEfficiency

isthepropertyofaresourceallocationofmaximizingthetotalsurplusreceivedbyallmembersofsociety.仁慈的社会计划者市场效率——资源配置使社会所有成员得到的总剩余最大化的性质。TheBenevolentSocialPlannerInadditiontomarketefficiency,asocialplannermightalsocareaboutequity

–thefairnessofthedistributionofwell-beingamongthevariousbuyersandsellers.仁慈的社会计划者除了效率之外，社会计划者还应关心平等——福利在各种买者与卖者之间分配的公平性。Figure7ConsumerandProducerSurplusintheMarketEquilibriumProducersurplusConsumersurplusPrice0QuantityEquilibriumpriceEquilibriumquantitySupplyDemandACBDE图7.市场均衡时的消费者与生产者剩余价格均衡价格0数量均衡数量A供给CB需求DE生产者剩余消费者剩余EvaluatingtheMarketEquilibriumThreeInsightsConcerningMarketOutcomesFreemarketsallocatethesupplyofgoodstothebuyerswhovaluethemmosthighly,asmeasuredbytheirwillingnesstopay.Freemarketsallocatethedemandforgoodstothesellerswhocanproducethematleastcost.Freemarketsproducethequantityofgoodsthatmaximizesthesumofconsumerandproducersurplus.市场均衡的评价三种关于市场结果的观点自由市场把物品的供给分配給对这些物品评价最高的买者。自由市场把物品的需求分配給可以以最低成本生产这些物品的卖者。自由市场生产使消费者和生产者总剩余最大化的产量。Figure8TheEfficiencyoftheEquilibriumQuantityQuantityPrice0SupplyDemandCosttosellersCosttosellersValuetobuyersValuetobuyersValuetobuyersisgreaterthancosttosellers.Valuetobuyersislessthancosttosellers.Equilibriumquantity价格0数量均衡数量供给需求卖者的成本买者的评价买者的评价卖者的成本买者的评价大于卖者的成本买者的评价小于卖者的成本图8.均衡数量的效率EvaluatingtheMarketEquilibriumBecausetheequilibriumoutcomeisanefficientallocationofresources,thesocialplannercanleavethemarketoutcomeashe/shefindsit.ThispolicyofleavingwellenoughalonegoesbytheFrenchexpressionlaissezfaire.市场均衡的评价因为均衡结果是资源的有效配置，所以社会计划者可以让市场自己找到结果。这种完全放开的政策可以用法语“自由放任”来表述，这句话字面上的含义是“让他们自由行事吧”。EvaluatingtheMarketEquilibriumMarketPowerIfamarketsystemisnotperfectlycompetitive,marketpowermayresult.Marketpoweristheabilitytoinfluenceprices.Marketpowercancausemarketstobeinefficientbecauseitkeepspriceandquantityfromtheequilibriumofsupplyanddemand.市场均衡的评价市场势力如果一个市场系统不是完全竞争的，就会出现市场势力。市场势力是影响市场价格的能力。市场势力可以使市场无效率，因为它使价格和数量背离供求均衡。EvaluatingtheMarketEquilibriumExternalitiescreatedwhenamarketoutcomeaffectsindividualsotherthanbuyersandsellersinthatmarket.causewelfareinamarkettodependonmorethanjustthevaluetothebuyersandcosttothesellers.Whenbuyersandsellersdonottakeexternalitiesintoaccountwhendecidinghowmuchtoconsumeandproduce,theequilibriuminthemarketcanbeinefficient.市场均衡的评价外部性当某一市场结果影响根本不参与此市场的人时，外部性就产生了。外部性使市场福利还要取决于买者评价和卖者成本之外的因素。在买者决定消费量和卖者决定生产量而不考虑外部性时，市场均衡可能是无效率的。Consumersurplusequalsbuyers’willingnesstopayforagoodminustheamounttheyactuallypayforit.Consumersurplusmeasuresthebenefitbuyersgetfromparticipatinginamarket.Consumersurpluscanbecomputedbyfindingtheareabelowthedemandcurveandabovetheprice.消费者剩余等于买者对某种物品的支付意愿减去买者的实际支付量。消费者剩余衡量买者从参与市场中得到的利益。消费者剩余可以通过找出需求曲线以下和价格以上的面积来计算。Producersurplusequalstheamountsellersreceivefortheirgoodsminustheircostsofproduction.Producersurplusmeasuresthebenefitsellersgetfromparticipatinginamarket.Producersurpluscanbecomputedbyfindingtheareabelowthepriceandabovethesupplycurve.生产者剩余等于卖者出售某种物品得到的量减去卖者的生产成本。生产者剩余衡量卖者从参与市场中得到的利益。生产者剩余可以通过找出价格以下和供给曲线以上的面积来计算。Anallocationofresourcesthatmaximizesthesumofconsumerandproducersurplusissaidtobeefficient.Policymakersareoftenconcernedwiththeefficiency,aswellastheequity,ofeconomicoutcomes.可以说使消费者和生产者剩余的总和最大化的资源配置是有效率的。政策制定者通常关心经济结果的效率以及平等。Theequilibriumofdemandandsupplymaximizesthesumofconsumerandproducersurplus.Thisisasiftheinvisiblehandofthemarketplaceleadsbuyersandsellerstoallocateresourcesefficiently.Marketsdonotallocateresourcesefficientlyinthepresenceofmarketfailures.供给与需求的均衡使消费者与生产者剩余的总和最大化。这就好像市场中看不见的手指引买者与卖者有效地配置资源。在存在市场势力或外部性这类市场失灵的情况下，市场不能有效地配置资源。©2007ThomsonSouth-Western应用：税收的成本Application:TheCostsofTaxationWelfareeconomicsisthestudyofhowtheallocationof

resourcesaffectseconomicwell-being.Buyersandsellersreceivebenefitsfromtakingpartinthemarket.Theequilibriuminamarketmaximizesthetotalwelfareofbuyersandsellers.应用:税收的成本福利经济学——研究资源配置如何影响经济福利。买者和卖者可以从参与市场活动中获得利益。市场均衡可以使买者和卖者的总利益最大化。THEDEADWEIGHTLOSSOFTAXATIONHowdotaxesaffecttheeconomicwell-beingofmarketparticipants?税收的无谓损失税收如何影响市场参与者的经济福利?THEDEADWEIGHTLOSSOFTAXATIONItdoesnotmatterwhetherataxonagoodisleviedonbuyersorsellers

ofthegood...theprice

paidbybuyersrises,and

thepricereceivedby

sellersfalls.税收的无谓损失一种物品的税收是向买者征收还是向卖者征收是不重要的…，结果都是买者支付的价格上升，而卖者得到的价格下降。Figure1TheEffectsofaTaxSizeoftaxQuantity0PricePricebuyerspayPricesellersreceiveDemandSupplyPricewithouttaxQuantitywithouttaxQuantitywithtaxThepricepaidbyconsumersishigherThepricereceivedbyfirmsislower.Andthequantitydeclines.Whobenefits?图1.税收效应税收规模数量0价格买者支付的价格卖者得到的价格需求供给没有税收时的价格税前数量税后数量消费者支付的价格更高了厂商得到的价格更低了而且数量下降.谁受益?HowaTaxAffectsMarketParticipantsAtaxplacesawedgebetweenthepricebuyerspayandthepricesellersreceive.Becauseofthistaxwedge,thequantitysoldfallsbelowthelevelthatwouldbesoldwithoutatax.Thesizeofthemarketforthatgoodshrinks.税收如何影响市场参与者税收在买者支付的价格和卖者得到的价格之间打入了一个楔子。由于这种税收楔子，销售量低于没有税收时应该达到的水平。对一种物品征税使这种物品的市场规模收缩HowaTaxAffectsMarketParticipantsTaxRevenueT=thesizeofthetaxQ=thequantityofthegoodsoldT

Q=thegovernment’staxrevenue税收如何影响市场参与者税收收入T=税收规模Q=物品销售量T

Q=政府的税收收入Figure2TaxRevenueTaxrevenue(T×Q)Sizeoftax(T)Quantitysold(Q)Quantity0PriceDemandSupplyQuantitywithouttaxQuantitywithtaxPricebuyerspayPricesellersreceive图2.税收收入价格0数量税前数量供给需求卖者得到的价格税后数量税收规模(T)销售量(Q)税收收入(TxQ)买者支付的价格Figure3HowaTaxEffectsWelfare

AFBDCE

Quantity0Price

DemandSupply=PBQ2=PSPricebuyerspayPricesellersreceive=P1Q1Pricewithouttax图3.税收如何影响福利数量0价格需求供给Q1ABCFDEQ2征税减少了消费者剩余(用面积B+C代表)和生产者剩余(用面积D+E代表)税收=(B+D)买者支付的价格=PB

P1没有税收时的价格=

PS卖者得到的价格=无谓损失=(C+E)Figure3HowaTaxEffectsWelfare

AFBDCE

Quantity0Price

DemandSupply=PBQ2=PSPricebuyerspayPricesellersreceive=P1Q1Pricewithouttax图3.税收如何影响福利数量0价格需求供给Q1ABCFDEQ2买者支付的价格=PB

P1没有税收时的价格=

PS卖者得到的价格=HowaTaxAffectsWelfareWithoutTaxWithTaxChangeConsumerSurplusA+B+CA-(B+C)ProducerSurplusD+E+FF-(D+E)TaxRevenuenoneB+D+(B+D)TotalSurplusA+B+C+D+E+FA+B+D+F-(C+E)TheareaC+Eshowsthefallintotalsurplusandisthe

deadweightloss

ofthetax.税收如何影响福利没有税收时有税收时变动消费者剩余A+B+CA-(B+C)生产者剩余D+E+FF-(D+E)税收收入无B+D+(B+D)总剩余A+B+C+D+E+FA+B+D+F-(C+E)C+E的面积表示总剩余减少，而且是税收的无谓损失。HowaTaxAffectsMarketParticipantsChangesinWelfareAdeadweightlossisthefallintotalsurplusthatresultsfromamarketdistortion,suchasatax.税收如何影响市场参与者福利的变化无谓损失——市场扭曲（比如收税）引起的总剩余减少。HowaTaxAffectsMarketParticipantsThechangeintotalwelfareincludes:Thechangeinconsumersurplus,Thechangeinproducersurplus,andThechangeintaxrevenue.Thelossestobuyersandsellersexceedtherevenueraisedbythegovernment.Thisfallintotalsurplusiscalledthedeadweightloss.税收如何影响市场参与者总福利的变动包括：消费者剩余的变动生产者剩余的变动税收收入的变动买者和卖者由税收受到的损失大于政府筹集到的收入无谓损失——税收引起的总剩余减少DeadweightLossesandtheGainsfromTradeTaxescausedeadweightlossesbecausetheypreventbuyersandsellersfromrealizingsomeofthegainsfromtrade.无谓损失与贸易的好处税收引起无谓损失是因为它使买者与卖者不能实现某些贸易的好处。Figure4TheDeadweightLossCosttosellersValuetobuyersSizeoftaxQuantity0PriceDemandSupplyLostgainsfromtradeReductioninquantityduetothetaxPricewithouttaxQ1PBQ2PS图4.无谓损失

数量0价格

需求供给Q1PB没有税收P1时的价格PSQ2税收规模损失的贸易好处卖者的成本买者的评价由于税收引起的数量减少THEDETERMINANTSOFTHEDEADWEIGHTLOSSWhatdetermineswhetherthedeadweightlossfromataxislargeorsmall?Themagnitudeofthedeadweightlossdependsonhowmuchthequantitysuppliedandquantitydemandedrespondtochangesintheprice.That,inturn,dependsonthepriceelasticitiesofsupplyanddemand.无谓损失的决定因素什么因素决定税收的无谓损失是大还是小？无谓损失的大小决定于供給量和需求量对价格变动的反应程度。也就是说，决定于供给和需求的价格弹性。Figure5TaxDistortionsandElasticities(a)InelasticSupplyPrice0QuantityDemandSupplySizeoftaxWhensupplyisrelativelyinelastic,thedeadweightlossofataxissmall.图5.税收扭曲与弹性(a)缺乏弹性的供给价格0数量需求供给税收规模当供给比较缺乏弹性时，税收的无谓损失小。Figure5TaxDistortionsandElasticities(b)ElasticSupplyPrice0QuantityDemandSupplySizeoftaxWhensupplyisrelativelyelastic,thedeadweightlossofataxislarge.图5.税收扭曲与弹性(b)富有弹性的供给价格0数量需求供给税收规模当供给比较富有弹性时，税收无谓损失大Figure5TaxDistortionsandElasticitiesDemandSupply(c)InelasticDemandPrice0QuantitySizeoftaxWhendemandisrelativelyinelastic,thedeadweightlossofataxissmall.图5.税收扭曲与弹性需求供给(c)缺乏弹性的需求价格0数量税收规模当需求比较缺乏弹性时，税收的无谓损失小。Figure5TaxDistortionsandElasticities(d)ElasticDemandPrice0QuantitySizeoftaxDemandSupplyWhendemandisrelativelyelastic,thedeadweightlossofataxislarge.图5.税收扭曲与弹性(d)富有弹性的需求价格0数量税收规模需求供给当需求比较富有弹性时，税收的无谓损失大。THEDETERMINANTSOFTHEDEADWEIGHTLOSSThegreatertheelasticitiesofdemandandsupply:thelargerwillbethedeclineinequilibriumquantityand,thegreaterthedeadweightlossofatax.无谓损失的决定因素供给和需求的弹性越大：均衡数量下降的越多，税收的无谓损失也就越大。DEADWEIGHTLOSSANDTAXREVENUEASTAXESVARYTheDeadweightLossDebateSomeeconomistsarguethatlabortaxesarehighlydistortingandbelievethatlaborsupplyismoreelastic.Someexamplesofworkerswhomayrespondmoretoincentives:WorkerswhocanadjustthenumberofhourstheyworkFamilieswithsecondearnersElderlywhocanchoosewhentoretireWorkersintheundergroundeconomy(i.e.,thoseengaginginillegalactivity)无谓损失和税收收入随税收变动而变动无谓损失的争论一些经济学家认为劳动税引起严重扭曲，他们相信劳动供给是较为富有弹性的.一些对激励反应较大的工人:许多可以调整工作时间长短的工人一些有第二个赚钱人的家庭许多老年人可以选择什么时候退休从事地下经济活动的工人(如从事非法活动的人)DEADWEIGHTLOSSANDTAXREVENUEASTAXESVARYWitheachincreaseinthetaxrate,thedeadweightlossofthetaxrisesevenmorerapidlythanthesizeofthetax.无谓损失和税收收入随税收规模而变动随着每一次税率增加，税收无谓损失的增加要快于税收规模。Figure6HowDeadweightLossandTaxRevenueVarywiththeSizeoftheTaxTaxrevenueDemandSupplyQuantity0PriceQ1(a)SmallTaxDeadweightlossPBQ2PS图6.无谓损失和税收收入如何随着税收规模而变动税收收入需求供给数量0价格Q1(a)小额税无谓损失PBQ2PSFigure6HowDeadweightLossandTaxRevenueVarywiththeSizeoftheTaxTaxrevenueQuantity0Price(b)MediumTaxPBQ2PSSupplyDemandQ1Deadweightloss图6.无谓损失和税收收入如何随着税收规模而变动税收收入数量0价格(b)中额税PBQ2PS供给需求Q1无谓损失Figure6HowDeadweightLossandTaxRevenueVarywiththeSizeoftheTaxTaxrevenueDemandSupplyQuantity0PriceQ1(c)LargeTaxPBQ2PSDeadweightloss图6.无谓损失和税收收入如何随着税收规模而变动税收收入需求供给数量0价格Q1(c)大额税PBQ2PS无谓损失DEADWEIGHTLOSSANDTAXREVENUEASTAXESVARYForthesmalltax,taxrevenueissmall.Asthesizeofthetaxrises,taxrevenuegrows.Butasthesizeofthetaxcontinuestorise,taxrevenuefallsbecausethehighertaxreducesthesizeofthemarket.无谓损失和税收收入随税收变动而变动收小额税时，税收收入少。随着税收规模增加，税收收入增加。但随着税收规模继续增加，税收收入反而减少，这是因为较高的税收规模减少了更多的市场规模。Figure6HowDeadweightLossandTaxRevenueVarywiththeSizeofaTax(a)DeadweightLossDeadweightLoss0TaxSize图6.无谓损失和税收收入如何随着税收规模而变动无谓损失无谓损失0税收规模Figure6HowDeadweightLossandTaxRevenueVarywiththeSizeofaTax(b)Revenue(theLaffercurve)TaxRevenue0TaxSize图6.无谓损失和税收收入如何随着税收规模而变动(b)税收收入（拉伐曲线）税收收入0税收规模DEADWEIGHTLOSSANDTAXREVENUEASTAXESVARYAsthesizeofataxincreases,itsdeadweightlossquicklygetslarger.Bycontrast,taxrevenuefirstriseswiththesizeofatax,butthen,asthetaxgetslarger,themarketshrinkssomuchthattaxrevenuestartstofall.无谓损失和税收收入随税收变动而变动随着税收规模提高，无谓损失迅速增大。相反，随着税收规模提高，税收收入先是增加，然后随着税收规模越来越大，市场规模收缩非常之大，以至于税收收入开始减少。Ataxonagoodreducesthewelfareofbuyersandsellersofthegood,andthereductioninconsumerandproducersurplususuallyexceedstherevenuesraisedbythegovernment.Thefallintotalsurplus—thesumofconsumersurplus,producersurplus,andtaxrevenue—iscalledthedeadweightlossofthetax.向一种物品征税减少了该物品买者与卖者的福利，而且消费者和生产者剩余的减少通常超过了政府筹集到的收入。总剩余（消费者剩余、生产者剩余和税收收入之和）的减少被称为税收的无谓损失。Taxeshaveadeadweightlossbecausetheycausebuyerstoconsumelessandsellerstoproduceless.Thischangeinbehaviorshrinksthesizeofthemarketbelowthelevelthatmaximizestotalsurplus.税收有无谓损失是因为它引起买者少消费和卖者少生产。这种行为变化使市场规模缩小到使总剩余最大化的水平之下。Asataxgrowslarger,itdistortsincentivesmore,anditsdeadweightlossgrowslarger.Taxrevenuefirstriseswiththesizeofatax.Eventually,however,alargertaxreducestaxrevenuebecauseitreducesthesizeofthemarket.随着税收增加，它对激励的扭曲越来越大，而且无谓损失也越来越大。税收收入起初随着税收规模增加而增加。但是，最终由于高税收减少了市场规模，也就减少了税收收入。©2007ThomsonSouth-Western应用：国际贸易Application:InternationalTradeWhatdetermineswhetheracountryimportsorexportsagood?Whogainsandwholosesfromfreetradeamongcountries?Whataretheargumentsthatpeopleusetoadvocatetraderestrictions?应用：国际贸易什么决定一个国家是否进口或出口一种物品?在国际自由贸易中谁获利谁亏损？人们用来支持贸易限制的各种观点是什么？THEDETERMINANTSOFTRADEEquilibriumWithoutTradeAssume:Acountryisisolatedfromrestoftheworldandproducessteel.Themarketforsteelconsistsofthebuyersandsellersinthecountry.Nooneinthecountryisallowedtoimportorexportsteel.贸易的决定因素没有贸易时的均衡假定:一个生产钢铁的国家孤立于其他国家钢铁市场由这个国家的买者和卖者组成这个国家的如何人都不允许进口或出口钢铁Figure1TheEquilibriumwithoutInternationalTradeConsumersurplusProducersurplusPriceofSteel0QuantityofSteelDomesticsupplyDomesticdemandEquilibriumpriceEquilibriumquantity0图1.没有国际贸易时的均衡钢铁的价格均衡价格0钢铁数量均衡数量国内供给国内需求生产者剩余消费者剩余TheEquilibriumWithoutTradeResults:Domesticpriceadjuststobalancedemandandsupply.Thesumofconsumerandproducersurplusmeasuresthetotalbenefitsthatbuyersandsellersreceive.0没有贸易时的均衡结果:国内价格调整使国内卖者的供給量与国内买者的需求量平衡。消费者剩余和生产者剩余的总和来衡量买者和卖者从钢铁市场上得到的总利益。0TheWorldPriceandComparativeAdvantage

世界价格与比较优势Ifthecountrydecidestoengageininternationaltrade,willitbeanimporterorexporterofsteel?如果这个国家决定参与国际贸易，它将是钢铁进口国还是出口国？TheWorldPriceandComparativeAdvantageTheeffectsoffreetradecanbeshownbycomparingthedomesticpriceofagoodwithouttradeandtheworldpriceofthegood.Theworldpricereferstothepricethatprevailsintheworldmarketforthatgood.世界价格与比较优势自由贸易的效果可以从没有贸易时国内物品价格与世界价格相比较中得到说明。世界价格——一种物品在世界市场上所流行的价格。TheWorldPriceandComparativeAdvantageIfacountryhasacomparativeadvantage,thenthedomesticpricewillbebelowtheworldprice,andthecountrywillbeanexporterofthegood.Ifthecountrydoesnothaveacomparativeadvantage,thenthedomesticpricewillbehigherthantheworldprice,andthecountrywillbeanimporterofthegood.世界价格与比较优势如果一个国家有比较优势，那么国内价格将比世界价格低，这个国家就会是该物品的出口国。如果一个国家没有比较优势，那么国内价格将比世界价格高，这个国家就会是该物品的进口国。Figure2InternationalTradeinanExportingCountryPriceofSteel0QuantityofSteelDomesticsupplyPriceaftertradeWorldpriceDomesticdemandExportsPricebeforetradeDomesticquantitydemandedDomesticquantitysupplied钢铁价格0钢铁数量国内需求图2.出口国的国际贸易国内供给世界价格贸易后的价格出口国内需求量国内供給量贸易前的价格Figure2InternationalTradeinanExportingCountryDCBAPriceofSteel0QuantityofSteelDomesticsupplyPriceaftertradeWorldpriceDomesticdemandExportsPricebeforetrade图2.出口国的国际贸易DCBA0钢铁数量国内供给贸易后的价格世界价格国内需求出口贸易前的价格钢铁价格Figure2InternationalTradeinanExportingCountryDCBAPriceofSteel0QuantityofSteelDomesticsupplyPriceaftertradeWorldpriceDomesticdemandExportsPricebeforetradeProducersurplusbeforetradeConsumersurplusbeforetradeCConsumersurplusaftertradeBProducersurplusaftertrade0图2.出口国的国际贸易DCBA钢铁价格0钢铁数量国内供给贸易后的价格世界价格国内需求出口贸易前的价格贸易前的生产者剩余贸易前的消费者剩余C贸易后的消费者剩余B贸易后的生产者剩余0HowFreeTradeAffectsWelfareinanExportingCountry0自由贸易如何影响出口国的福利面积D表示总剩余增加，并代表贸易的利益贸易前贸易后变化消费者剩余A+BA-B生产者剩余CB+C+D+(B+D)总剩余A+B+CA+B+C+D+DTHEWINNERSANDLOSERSFROMTRADETheanalysisofanexportingcountryyieldstwoconclusions:Domesticproducersofthegoodarebetteroff,anddomesticconsumersofthegoodareworseoff.Traderaisestheeconomicwell-beingofthenationasawhole.自由贸易的赢家和输家对出口国的分析得出了两个结论：当一国允许贸易并成为一种物品的出口国时，该物品的国内生产者状况变好，而该物品的国内消费者状况变坏。贸易增加了一国的整体经济福利。TheGainsandLossesofanImportingCountry

InternationalTradeinanImportingCountryIftheworldpriceofsteelislowerthanthedomesticprice,thecountrywillbeanimporterofsteelwhentradeispermitted.domesticconsumerswillwanttobuysteelatthelowerworldprice.domesticproducersofsteelwillhavetolowertheiroutputbecausethedomesticpricemovestotheworldprice.进口国的得失进口国的国际贸易如果世界价格低于国内价格，一旦允许自由贸易，该国家将是钢铁进口国。国内消费者就想以比国内价格更低的世界价格购买钢铁。因为国内价格移向世界价格，所以国内钢铁生产者不得不降低产量。Figure3InternationalTradeinanImportingCountryPriceofSteel0QuantityPriceaftertradeWorldpriceofSteelDomesticsupplyDomesticdemandImportsDomesticquantitysuppliedDomesticquantitydemandedPricebeforetrade图3.进口国的国际贸易钢铁价格0钢铁数量国内供给国内需求世界价格贸易后的价格国内供给量国内需求量贸易前的价格进口Figure3InternationalTradeinanImportingCountryCBDAPriceofSteel0QuantityofSteelDomesticsupplyDomesticdemandPriceaftertradeWorldpriceImportsPricebeforetradeConsumersurplusbeforetradeProducersurplusbeforetrade图3.进口国的国际贸易CBDA钢铁价格0钢铁数量国内供给国内需求贸易后的价格世界价格进口贸易前的价格贸易前的消费者剩余贸易前的生产者剩余Figure3InternationalTradeinanImportingCountryCBDAPriceofSteel0QuantityofSteelPriceaftertradeWorldpriceProducersurplusaftertradeConsumersurplusaftertradeDBDomesticdemandDomesticsupplyImportsPricebeforetrade图3.进口国的国际贸易CBDA0贸易后的生产者剩余贸易后的消费者剩余DB钢铁数量世界价格国内供给钢铁价格贸易前的价格贸易后的价格进口HowFreeTradeAffectsWelfareinanImportingCountry自由贸易如何影响进口国的福利面积D表示总剩余的增加量，并代表贸易的收益贸易前贸易后变化消费者剩余AA+B+D+(B+D)生产者剩余B+CC-B总剩余A+B+CA+B+C+D+DTheGainsandLossesofanImportingCountryHowFreeTradeAffectsWelfareinanImportingCountryTheanalysisofanimportingcountryyieldstwoconclusions:Domesticproducersofthegoodareworseoff,anddomesticconsumersofthegoodarebetteroff.Traderaisestheeconomicwell-beingofthenationasawholebecausethegainsofconsumersexceedthelossesofproducers.进口国的得失自由贸易如何影响进口国的福利对进口国的分析得出了两个结论:当一国允许自由贸易并成为一种物品的进口国时，该物品的国内消费者状况变好，而该物品的国内生产者状况变坏。贸易增加了一国的整体经济福利。THEWINNERSANDLOSERSFROMTRADEThegainsofthewinnersexceedthelossesofthelosers.Thenetchangeintotal

surplusispositive.国际自由贸