7消费者生产者与生产效率英文版

Consumers,Producers,

andtheEfficiencyofMarkets7消费者、生产者

与市场效率Inthischapter,

lookfortheanswerstothesequestions:Whatisconsumersurplus(消费者剩余)?Howisitrelatedtothedemandcurve?Whatisproducersurplus（生产者剩余）?Howisitrelatedtothesupplycurve?Domarketsproduceadesirableallocationofresources（市场配置资源的合意配置）?Orcouldthemarketoutcomebeimprovedupon?1SomenormativequestionsTheconsumershopeforalowerpriceallthetime,andtheproducershopeforahigherprice.Shouldthepricebelowerorhigher?Whatisthe“good”price?Whatistheproperwaytousetheresource?Whoshouldconsumemoregoods?Isclearance（出清）thebestresultofmarket?Whatisthevalueofthemarket?CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS2CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS3Ismarketeconomygood?Theallocationofresources

（资源配置）refersto:howmuchofeachgoodisproducedwhichproducersproduceitwhichconsumersconsumeitInmarketeconomies,theforcesofsupplyanddemanddeterminethepricesofgoodsandservicesandthequantitiessold.Themarketcouldclearbyitself,butisitagoodresult?CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS4WelfareEconomics福利经济学Welfareeconomicsstudieshowtheallocationofresourcesaffectseconomicwell-being（经济福利）.Whatbenefitsdothebuyersandsellersgetfromtakingpartinamarket?Whatarethetotalbenefitsofthemarket?Howsocietycanmakethesebenefitsaslargeaspossible?Aprofoundconclusion:Theequilibriumofsupplyanddemandinamarketmaximizesthetotalbenefitsreceivedbybuyersandsellers.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS5WillingnesstoPayandValue

买者的支付意愿和价值Abuyer’swillingnesstopay(WTP)foragoodisthemaximumamountthebuyerwillpayforthatgood.WTPmeasureshowmuchthebuyervaluesthegood.nameWTPAnthony安东尼$250Chad查德175Flea300John125Example:

4buyers’WTP

foraniPodCONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS6WTPandtheDemandCurveQ:

IfpriceofiPodis$200,whowillbuyaniPod,andwhatisquantitydemanded?A: Anthony&FleawillbuyaniPod,Chad&Johnwillnot. Hence,Qd=2

whenP=$200.nameWTPAnthony$250Chad175Flea300John125CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS7WTPandtheDemandCurveDerivethedemandschedule:4John,Chad,

Anthony,Flea0–1253Chad,Anthony,

Flea126–1752Anthony,Flea176–2501Flea251–3000nobody$301&upQdwhobuysP(price

ofiPod)nameWTPAnthony$250Chad175Flea300John125CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS8WTPandtheDemandCurvePQd$301&up0251–3001176–2502126–17530–1254PQCONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS9AbouttheStaircaseShape…ThisDcurvelookslikeastaircase

with4steps–oneperbuyer.PQIftherewereahuge#ofbuyers,asinacompetitivemarket,therewouldbeahuge#

ofverytinysteps,anditwouldlookmorelikeasmoothcurve.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS10WTPandtheDemandCurveAtanyQ,

theheightof

theDcurveistheWTPofthemarginalbuyer边际购买者thebuyerwhowouldleavethemarketifPwereanyhigher.PQFlea’sWTPAnthony’sWTPChad’sWTPJohn’s

WTPCONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS11ConsumerSurplus(CS)消费者剩余Consumersurplusistheamountabuyeriswillingtopayminustheamountthebuyeractuallypays:

CS=WTP–PnameWTPAnthony$250Chad175Flea300John125SupposeP=$260.Flea’sCS=$300–260=$40.TheothersgetnoCSbecausetheydonotbuyaniPodatthisprice.TotalCS=$40.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS12CSandtheDemandCurvePQFlea’sWTPP=$260Flea’sCS=

$300–260=$40TotalCS=$40CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS13CSandtheDemandCurvePQFlea’sWTPAnthony’sWTPInstead,suppose

P=$220Flea’sCS=

$300–220=$80Anthony’sCS=

$250–220=$30TotalCS=$110CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS14CSandtheDemandCurvePQThelesson:TotalCSequalstheareaunder

thedemandcurveabovetheprice,from0toQ.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS15PQ$CSwithLotsofBuyers&aSmoothDCurveThedemandforshoesD1000sofpairsofshoesPrice

perpairAtQ=5(thousand),themarginalbuyeriswillingtopay$50forpairofshoes.SupposeP=$30.Thenhisconsumersurplus=$20.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS16PQCSwithLotsofBuyers&aSmoothDCurveThedemandforshoesDCSistheareab/wPandtheDcurve,from0toQ.Recall:areaof

atriangleequals

½xbasexheightHeight=

$60–30=$30.So,

CS=½x15x$30

=$225.h$CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS17PQHowaHigherPriceReducesCSDIfPrisesto$40,CS=½x10x$20

=$100.TworeasonsforthefallinCS.1. FallinCS

duetobuyersleavingmarket2. FallinCSduetoremainingbuyers

payinghigherPSomenotesonCSTheCSequalstoWTPminustheactualpay.itmeasuresthebenefitthatbuyersreceivefromagoodasthebuyersthemselvesperceiveit.

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。CSisagoodmeasureifpreferencesofbuyersshouldberespectedallthetime.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS18But,sometimes,theWTP(perceivedvalue,感知价值)maybedifferentfromtherealvalue.TheCSisnotagoodmeasureinthiscase.Inmostcase,especiallyundertherationalassumption,CSworksquitewell.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS1920PQdemandcurveA.

Findmarginalbuyer’sWTPat

Q=10.B.

FindCSfor

P=$30.SupposePfallsto$20.

HowmuchwillCSincreasedueto…C.

buyersentering

themarketD.

existingbuyerspayinglowerprice$ACTIVELEARNING1

ConsumersurplusACTIVELEARNING1

Answers21P$QdemandcurveA. AtQ=10,marginalbuyer’sWTPis$30.B.

CS=½x10x$10

=$50Pfallsto$20.C.CSforthe

additionalbuyers

=½x10x$10=$50D.IncreaseinCS

oninitial10units

=10x$10=$100CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS22CostandtheSupplyCurvenamecostJack杰克$10Janet珍妮特20Chrissy克丽希35Asellerwillproduceandsellthegood/serviceonlyifthe

priceexceedshisorhercost.Hence,costisameasureofwillingnesstosell.Costisthevalueofeverythingasellermustgiveuptoproduceagood(i.e.,opportunitycost).Includescostofallresourcesusedtoproducegood,includingvalueoftheseller’stime.Example:Costsof3sellersinthelawn-cutting（修草）business.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS23CostandtheSupplyCurve335&up220–34110–190$0–9QsPDerivethesupplyschedulefromthecostdata:namecostJack$10Janet20Chrissy35CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS24CostandtheSupplyCurvePQPQs$0–9010–19120–34235&up3CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS25CostandtheSupplyCurvePQAteachQ,

theheightof

theScurve

isthecostofthemarginalseller（边际卖家）,

thesellerwhowouldleave

themarketif

thepricewereanylower.Chrissy’s

costJanet’scostJack’scostCONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS26ProducerSurplus生产者剩余PQProducersurplus(PS):theamountaseller

ispaidforagood

minustheseller’scost生产者剩余——卖者得到的量减去卖者的成本。PS=P–costCONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS27ProducerSurplusandtheSCurvePQSupposeP=$25.Jack’sPS=$15Janet’sPS=$5Chrissy’sPS=$0TotalPS=$20Janet’s珍妮特costJack’s杰克costTotalPSequalstheareaabovethesupplycurveundertheprice,from0toQ.Chrissy’s

克丽希costPS=P–costCONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS28PQPSwithLotsofSellers&aSmoothSCurveThesupplyofshoesS1000sofpairsofshoesPrice

perpairSupposeP=$40.AtQ=15(thousand),themarginalseller’scostis$30,andherproducersurplusis$10.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS29PQPSwithLotsofSellers&aSmoothSCurveThesupplyofshoesSPSistheareab/w

PandtheScurve,from0toQ.Theheightofthistriangleis

$40–15=$25.So,

PS=½xbxh

=½x25x$25

=$312.50hCONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS30PQHowaLowerPriceReducesPSIfPfallsto$30,PS=½x15x$15

=$112.50TworeasonsforthefallinPS.S1. FallinPS

duetosellersleavingmarket2. FallinPSduetoremainingsellers

gettinglowerPPQsupplycurveA.

Findmarginal

seller’scost

atQ=10.B.

FindtotalPSfor

P=$20.SupposePrisesto$30.

Findtheincrease

inPSdueto…C.

selling5

additionalunitsD.

gettingahigherpriceontheinitial10units31ACTIVELEARNING2

ProducersurplusACTIVELEARNING2

AnswersPQsupplycurveA.AtQ=10,

marginalcost=$20

B.

PS=½x10x$20

=$100Prisesto$30.C. PSon

additionalunits

=½x5x$10=$25D.

IncreaseinPS

oninitial10units

=10x$10=$10032CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS33CS,PS,andTotalSurplus

消费者剩余，生产者剩余，总剩余CS=(valuetobuyers)–(amountpaidbybuyers) = buyers’gainsfromparticipatinginthemarketPS=(amountreceivedbysellers)–(costtosellers) =sellers’gainsfromparticipatinginthemarketTotalsurplus=CS+PS =totalgainsfromtradeinamarket =(valuetobuyers)–(costtosellers)CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS34PQ$DSCSofsinglebuyerPSofsinglesellerCSofallbuyersPSofallsellersSurplusofthemarketCS,PS,andTotalSurplus

消费者剩余，生产者剩余，总剩余CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS35TheMarket’sAllocationofResourcesInamarketeconomy,theallocationofresources

isdecentralized（权力下放）,determinedbytheinteractionsofmanyself-interestedbuyersandsellers.Isthemarket’sallocationofresourcesdesirable（合意）?Orwouldadifferentallocationofresourcesmakesocietybetteroff?Toanswerthis,weusetotalsurplusasameasureofsociety’swell-being,andweconsiderwhetherthemarket’sallocationisefficient.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS36TheBenevolentSocialPlanner

好心的社会管理者Thebenevolentsocialplannerisanall-knowing（全知）,all-powerful（全能）,well-intentioneddictator（目标明确的独裁者）.Theplannerwantstomaximizetheeconomicwell-beingofeveryoneinsociety.Toachievetheaim,theplannermustfirstdecidehowtomeasuretheeconomicwell-beingofasociety.Onepossiblemeasureisthesumofconsumerandproducersurplus,whichwecalltotalsurplus.thesocialplannermightalsocareaboutequality,thoughthefocushereisonefficiency.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS37EfficiencyAnallocationofresourcesisefficientifitmaximizestotalsurplus.Efficiencymeans:Thegoodsareconsumedbythebuyerswhovaluethemmosthighly.Thegoodsareproducedbytheproducerswiththelowestcosts.Raisingorloweringthequantityofagoodwouldnotincreasetotalsurplus.=(valuetobuyers)–(costtosellers)Total

surplusCONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS38EvaluatingtheMarketEquilibriumMarketeq’m:

P=$30

Q=15,000Totalsurplus

=CS+PSIsthemarketeq’mefficient?PQSDCSPSCONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS39WhichBuyersConsumetheGood?PQSDEverybuyer

whoseWTPis

≥$30willbuy.Everybuyer

whoseWTPis

<$30willnot.So,thebuyerswhovaluethegoodmosthighlyaretheoneswhoconsumeit.

CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS40WhichSellersProducetheGood?PQSDEverysellerwhosecostis≤$30willproducethegood.Everysellerwhosecostis>$30willnot.So,thesellerswiththelowestcostproducethegood.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS41DoesEq’mQMaximizeTotalSurplus?PQSDAtQ=20,

costofproducing

themarginalunit

is$35valuetoconsumers

ofthemarginalunit

isonly$20Hence,canincreasetotalsurplus

byreducingQ.ThisistrueatanyQgreaterthan15.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS42DoesEq’mQMaximizeTotalSurplus?PQSDAtQ=10,

costofproducing

themarginalunit

is$25valuetoconsumers

ofthemarginalunit

is$40Hence,canincreasetotalsurplus

byincreasingQ.ThisistrueatanyQlessthan15.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS43DoesEq’mQMaximizeTotalSurplus?PQSDThemarket

eq’mquantitymaximizes

totalsurplus:

Atanyotherquantity,

canincrease

totalsurplusbymovingtoward

themarketeq’mquantity.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS44Price0QuantityEquilibriumquantitySupplyDemandCosttosellersValuetobuyersValuetobuyers

CosttosellersValuetobuyersisgreaterthancosttosellers.Valuetobuyersislessthancosttosellers.TheEfficiencyoftheEquilibriumQuantityCONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS45AdamSmithandtheInvisibleHand“Manhasalmostconstantoccasionforthehelpofhisbrethren,anditisvainforhimtoexpectitfromtheirbenevolenceonly.AdamSmith,

1723-1790PassagesfromTheWealthofNations,1776Hewillbemorelikelytoprevailifhecaninteresttheirself-loveinhisfavor,andshowthemthatitisfortheirownadvantagetodoforhimwhatherequiresofthem…Itisnotfromthebenevolenceofthebutcher,thebrewer,orthebakerthatweexpectourdinner,butfromtheirregardtotheirowninterest….CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS46AdamSmithandtheInvisibleHand“Everyindividual…neitherintendstopromotethepublicinterest,norknowshowmuchheispromotingit….AdamSmith,

1723-1790PassagesfromTheWealthofNations,1776Heintendsonlyhisowngain,andheisinthis,asinmanyothercases,ledbyaninvisiblehandtopromoteanendwhichwasnopartofhisintention.Norisitalwaystheworseforthesocietythatitwasnopartofit.Bypursuinghisowninteresthefrequentlypromotes

thatofthesocietymoreeffectuallythanwhenhereallyintendstopromoteit.”aninvisiblehandCONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS47TheFreeMarketvs.GovtIntervention

自由市场Vs.政府干预

Themarketequilibriumisefficient.Nootheroutcomeachieveshighertotalsurplus.Govtcannotraisetotalsurplusbychangingthemarket’sallocationofresources.Laissezfaire,(Frenchfor“allowthemtodo”)自由主义:

thenotionthatgovtshouldnotinterferewith(干预)themarket.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS48TheFreeMarketvs.CentralPlanning

自由市场Vs.中央计划Supposeresourceswereallocatednotbythemarket,butbyacentralplannerwhocaresaboutsociety’swell-being. Toallocateresourcesefficientlyandmaximizetotalsurplus,theplannerwouldneedtoknoweveryseller’scostandeverybuyer’sWTPforeverygoodintheentireeconomy.Thisisimpossible,andwhycentrally-plannedeconomiesareneververyefficient.CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS49Discuss:

ShouldTherebeaMarketinOrgans（器官）?OnApril12,2001,thefrontpageoftheBostonGloberantheheadline“HowaMother’sLoveHelpedSaveTwoLives.”AwomanwhosenamedSusanStephenshasasonwhoneedsakidneytransplant.Whenthedoctorlearnedthatthemother’skidneywasnotcompatible（不相容）,heproposedanovelsolution:IfStephensdonatedoneofherkidneystoastranger,hersonwouldmovetothetopofthekidneywaitinglist.Themotheracceptedthedeal,andsoontwopatientshadthetransplanttheywerewaitingfor.Ifthemothercouldtradeakidneyforakidney,wouldthehospitalallowhertotradeakidneyforsomethingelse?CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS50Casestudy

StrongBooze:CriminalIncentives

烈酒：犯罪激励During1920'sProhibition,thesell,manufacture,andtransportationofalcoholwererestrictedorillegal.Prohibitionwassupposedtolowercrimeandcorruption,reducesocialproblems,lowertaxesneededtosupportprisonsandpoorhouses,andimprovehealthandhygiene（卫生学）inAmerica.Butitturnsoutthatalcoholbecamemoredangeroustoconsume;organizedcrimeblossomed（涌现）;courtsandprisonssystemsbecameoverloaded;andendemiccorruption（地区腐败）ofpoliceandpublicofficialsoccurred.Whydidtheprohibitionofthe1920’sfail?CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS51CONCLUSIONThischapterusedwelfareeconomicstodemonstrateoneoftheTenPrinciples:

Marketsareusuallyagoodwayto

organizeeconomicactivity.Importantnote:

Wederivedtheselessonsassuming

perfectlycompetitivemarkets（完全竞争市场）.Inotherconditionswewillstudyinlaterchapters,themarketmayfailtoallocateresourcesefficiently…CONSUMERS,PRODUCERS,ANDTHEEFFICIENCYOFMARKETS52CONCLUSIONSuchmarketfailuresoccurwhen:Abuyerorsellerhasmarketpower（市场势力）–theabilitytoaffectthemarketprice.Transactionshavesideeffects,calledexternalities（外部性）,thataffectbystanders.(example:pollution)Onesideofthetradersdoesn'thaveenoughinformationaboutthegoodsWe’llusewelfareeconomicstoseehowpublicpolicymayimproveonthemarketoutcomeinsuchcases.Despitethepossibilityofmarketfailure,theanalysisinthischapterappliesinmanymarkets,andtheinvisiblehandremainsextremelyimportant.Exercise1.