會(huì)計(jì)學(xué)1ChExternalities微觀(guān)范里安上海交通大學(xué)趙旭實(shí)用ExamplesofNegativeExternalitiesAirpollution.Waterpollution.Loudpartiesnextdoor.Trafficcongestion.Second-handcigarettesmoke.Increasedinsurancepremiumsduetoalcoholortobaccoconsumption.第1頁(yè)/共116頁(yè)ExamplesofPositiveExternalitiesAwell-maintainedpropertynextdoorthatraisesthemarketvalueofyourproperty.Apleasantcologneorscentwornbythepersonseatednexttoyou.Improveddrivinghabitsthatreduceaccidentrisks.Ascientificadvance.第2頁(yè)/共116頁(yè)ExternalitiesandEfficiencyCrucially,anexternalityimpactsathirdparty;i.e.somebodywhoisnotaparticipantintheactivitythatproducestheexternalcostorbenefit.第3頁(yè)/共116頁(yè)ExternalitiesandEfficiencyExternalitiescauseParetoinefficiency;typicallytoomuchscarceresourceisallocatedtoanactivitywhichcausesanegativeexternalitytoolittleresourceisallocatedtoanactivitywhichcausesapositiveexternality.第4頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsAnexternalitywillviewedasapurelypubliccommodity.Acommodityispurelypublicifitisconsumedbyeveryone(nonexcludability),andeverybodyconsumestheentireamountofthecommodity(nonrivalryinconsumption).E.g.abroadcasttelevisionprogram.第5頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesConsidertwoagents,AandB,andtwocommodities,moneyandsmoke.BothsmokeandmoneyaregoodsforAgentA.MoneyisagoodandsmokeisabadforAgentB.Smokeisapurelypubliccommodity.第6頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesAgentAisendowedwith$yA.AgentBisendowedwith$yB.Smokeintensityismeasuredonascalefrom0(nosmoke)to1(maximumconcentration).第7頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAyAMoneyandsmokeare

bothgoodsforAgentA.第8頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAyAMoneyandsmokeare

bothgoodsforAgentA.Better第9頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOB10SmokemByBMoneyisagoodandsmokeisabadforAgentB.Better第10頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOB10SmokemByBMoneyisagoodandsmokeisabadforAgentB.Better第11頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesWhataretheefficientallocationsofsmokeandmoney?第12頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAyAOB10SmokemByB第13頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAOB10SmokemByAyB第14頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAOB10SmokemByAyB第15頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAOB10SmokemByAyB第16頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAOB10SmokemByAyBEfficientallocations第17頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesSupposethereisnomeansbywhichmoneycanbeexchangedforchangesinsmokelevel.WhatthenisAgentA’smostpreferredallocation?Isthisallocationefficient?第18頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAOB10SmokemByAyBEfficientallocations第19頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAOB10SmokemByAyBEfficientallocationsA’schoices第20頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAOB10SmokemByAyBEfficientallocationsA’smost

preferredchoice

isinefficient第21頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesContinuetosupposethereisnomeansbywhichmoneycanbeexchangedforchangesinsmokelevel.WhatisAgentB’smostpreferredallocation?Isthisallocationefficient?第22頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAOB10SmokemByAyBEfficientallocationsB’schoices第23頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAOB10SmokemByAyBEfficientallocationsB’smost

preferredchoice第24頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesOA10SmokemAOB10SmokemByAyBEfficientallocationsB’smost

preferredchoice

isinefficient第25頁(yè)/共116頁(yè)Inefficiency&NegativeExternalitiesSoifAandBcannottrademoneyforchangesinsmokeintensity,thentheoutcomeisinefficient.Eitherthereistoomuchsmoke(A’smostpreferredchoice)orthereistoolittlesmoke(B’schoice).第26頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsRonaldCoase’sinsightisthatmostexternalityproblemsareduetoaninadequatespecificationofpropertyrightsand,consequently,anabsenceofmarketsinwhichtradecanbeusedtointernalizeexternalcostsorbenefits.第27頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsCausingaproducerofanexternalitytobearthefullexternalcostortoenjoythefullexternalbenefitiscalledinternalizingtheexternality.第28頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsNeitherAgentAnorAgentBownstheairintheirroom.Whathappensifthispropertyrightiscreatedandisassignedtooneofthem?第29頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsSupposeAgentBisassignedownershipoftheairintheroom.AgentBcannowsell“rightstosmoke”.Willtherebeanysmoking?Ifso,howmuchsmokingandwhatwillbethepriceforthisamountofsmoke?第30頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsLetp(sA)bethepricepaidbyAgentAtoAgentBinordertocreateasmokeintensityofsA.第31頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyB第32頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyB第33頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyBp(sA)sA第34頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyBp(sA)Bothagentsgainandthereisapositiveamountofsmoking.sA第35頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyBp(sA)sAEstablishingamarketfortradingrightstosmokecausesanefficientallocationtobeachieved.第36頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsSupposeinsteadthatAgentAisassignedtheownershipoftheairintheroom.AgentBcannowpayAgentAtoreducethesmokeintensity.Howmuchsmokingwilltherebe?HowmuchmoneywillAgentBpaytoAgentA?第37頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyB第38頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyB第39頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyBsBp(sB)第40頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyBp(sB)Bothagentsgainandthereisareducedamountofsmoking.sB第41頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyBp(sB)Establishingamarketfortradingrightstoreduce

smokecausesanefficientallocationtobeachieved.sB第42頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsNoticethattheagentgiventhepropertyright(asset)isbetteroffthanatherownmostpreferredallocationintheabsenceofthepropertyright.amountofsmokingthatoccursinequilibriumdependsuponwhichagentisassignedthepropertyright.第43頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyBp(sB)p(sA)sA

1sBsBsA第44頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsIsthereacaseinwhichthesameamountofsmokingoccursinequilibriumnomatterwhichagentisassignedownershipoftheairintheroom?第45頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokemAOB10SmokemByAyBp(sB)p(sA)sA=sB第46頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokeOB10SmokeyAyBp(sB)p(sA)sA=sBForbothagents,theMRSisconstantas

moneychanges,forgivensmokeintensity.第47頁(yè)/共116頁(yè)ExternalitiesandPropertyRightsOA10SmokeOB10SmokeyAyBp(sB)p(sA)sA=sBSo,forbothagents,preferencesmustbe

quasilinearinmoney;U(m,s)=m+f(s).第48頁(yè)/共116頁(yè)Coase’sTheoremCoase’sTheoremis:Ifallagents’preferencesarequasilinearinmoney,thentheefficientleveloftheexternalitygeneratingcommodityisproducednomatterwhichagentisassignedthepropertyright.第49頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesAsteelmillproducesjointlysteelandpollution.Thepollutionadverselyaffectsanearbyfishery.Bothfirmsareprice-takers.pSisthemarketpriceofsteel.pFisthemarketpriceoffish.第50頁(yè)/共116頁(yè)P(yáng)roductionExternalitiescS(s,x)isthesteelfirm’scostofproducingsunitsofsteeljointlywithxunitsofpollution.Ifthesteelfirmdoesnotfaceanyoftheexternalcostsofitspollutionproductionthenitsprofitfunctionis

andthefirm’sproblemisto第51頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesThefirst-orderprofit-maximization

conditionsare第52頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesThefirst-orderprofit-maximization

conditionsareand第53頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesstatesthatthesteelfirmshouldproducetheoutputlevelofsteelforwhichprice=marginalproductioncost.第54頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesstatesthatthesteelfirmshouldproducetheoutputlevelofsteelforwhichprice=marginalproductioncost.istherateatwhichthefirm’sinternalproductioncostgoesdownasthepollutionlevelrises第55頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesstatesthatthesteelfirmshouldproducetheoutputlevelofsteelforwhichprice=marginalproductioncost.istherateatwhichthefirm’sinternalproductioncostgoesdownasthepollutionlevelrises,soisthemarginalcosttothefirmofpollutionreduction.第56頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesisthemarginalcosttothefirmofpollutionreduction.Whatisthemarginalbenefittothesteelfirmfromreducingpollution?第57頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesisthemarginalcosttothefirmofpollutionreduction.Whatisthemarginalbenefittothesteelfirmfromreducingpollution?Zero,sincethefirmdoesnotfaceitsexternalcost.Hencethesteelfirmchoosesthepollutionlevelforwhich第58頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesandthefirst-orderprofit-maximization

conditionsareandE.g.supposecS(s,x)=s2+(x-4)2and

pS=12.Then第59頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesdeterminestheprofit-max.outputlevelofsteel;s*=6.第60頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesdeterminestheprofit-max.outputlevelofsteel;s*=6.isthemarginalcosttothefirmfrompollutionreduction.Sinceitgetsnobenefitfromthisitsetsx*=4.第61頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesdeterminestheprofit-max.outputlevelofsteel;s*=6.isthemarginalcosttothefirmfrompollutionreduction.Sinceitgetsnobenefitfromthisitsetsx*=4.Thesteelfirm’smaximumprofitlevelis

thus第62頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesThecosttothefisheryofcatchingfunitsoffishwhenthesteelmillemitsxunitsofpollutioniscF(f,x).Givenf,cF(f,x)increaseswithx;i.e.thesteelfirminflictsanegativeexternalityonthefishery.第63頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesThecosttothefisheryofcatchingfunitsoffishwhenthesteelmillemitsxunitsofpollutioniscF(f,x).Givenf,cF(f,x)increaseswithx;i.e.thesteelfirminflictsanegativeexternalityonthefishery.Thefishery’sprofitfunctionis

sothefishery’sproblemisto第64頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesThefirst-orderprofit-maximization

conditionis第65頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesThefirst-orderprofit-maximization

conditionis第66頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesThefirst-orderprofit-maximization

conditionisHigherpollutionraisesthefishery’s

marginalproductioncostandlowersboth

itsoutputlevelanditsprofit.Thisistheexternalcostofthepollution.第67頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesE.g.supposecF(f;x)=f2+xfandpF=10.

Theexternalcostinflictedonthefisherybythesteelfirmisxf.Sincethefisheryhasnocontroloverxitmusttakethesteelfirm’schoiceofxasagiven.Thefishery’sprofitfunctionisthus第68頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesGivenx,thefirst-orderprofit-maximization

conditionis第69頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesGivenx,thefirst-orderprofit-maximization

conditionisSo,givenapollutionlevelxinflictedupon

it,thefishery’sprofit-maximizingoutput

levelis第70頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesGivenx,thefirst-orderprofit-maximization

conditionisSo,givenapollutionlevelxinflictedupon

it,thefishery’sprofit-maximizingoutput

levelisNoticethatthefisheryproducesless,and

earnslessprofit,asthesteelfirm’s

pollutionlevelincreases.第71頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesThesteelfirm,ignoringits

externalcostinflicteduponthefishery,

choosesx*=4,sothefishery’s

profit-maximizingoutputlevelgiventhe

steelfirm’schoiceofpollutionlevelis

f*=3,givingthefisheryamaximum

profitlevelofNoticethattheexternalcostis$12.第72頁(yè)/共116頁(yè)P(yáng)roductionExternalitiesArethesechoicesbythetwofirmsefficient?Whenthesteelfirmignorestheexternalcostsofitschoices,thesumofthetwofirm’sprofitsis$36+$9=$45.Is$45thelargestpossibletotalprofitthatcanbeachieved?第73頁(yè)/共116頁(yè)MergerandInternalizationSupposethetwofirmsmergetobecomeone.Whatisthehighestprofitthisnewfirmcanachieve?第74頁(yè)/共116頁(yè)MergerandInternalizationSupposethetwofirmsmergetobecomeone.Whatisthehighestprofitthisnewfirmcanachieve?

Whatchoicesofs,fandxmaximizethenewfirm’sprofit?第75頁(yè)/共116頁(yè)MergerandInternalizationThefirst-orderprofit-maximization

conditionsareThesolutionis第76頁(yè)/共116頁(yè)MergerandInternalizationAndthemergedfirm’smaximumprofit

levelisThisexceeds$45,thesumofthenon-mergedfirms.第77頁(yè)/共116頁(yè)MergerandInternalizationMergerhasimprovedefficiency.Onitsown,thesteelfirmproducedx*=4unitsofpollution.Withinthemergedfirm,pollutionproductionisonlyxm=2units.Somergerhascausedbothanimprovementinefficiencyandlesspollutionproduction.Why?第78頁(yè)/共116頁(yè)MergerandInternalizationThesteelfirm’sprofitfunctionissothemarginalcostofproducingxunitsofpollutionisWhenitdoesnothavetofacetheexternalcostsofitspollution,thesteelfirmincreasespollutionuntilthismarginalcostiszero;hencex*=4.第79頁(yè)/共116頁(yè)MergerandInternalizationInthemergedfirmtheprofitfunctionisThemarginalcostofpollutionisthus第80頁(yè)/共116頁(yè)MergerandInternalizationInthemergedfirmtheprofitfunctionisThemarginalcostofpollutionis第81頁(yè)/共116頁(yè)MergerandInternalizationInthemergedfirmtheprofitfunctionisThemarginalcostofpollutionisThemergedfirm’smarginalpollutioncostislargerbecauseitfacesthefullcostofitsownpollutionthroughincreasedcostsofproductioninthefishery,solesspollutionisproducedbythemergedfirm.第82頁(yè)/共116頁(yè)MergerandInternalizationButwhyisthemergedfirm’spollutionlevelofxm=2efficient?第83頁(yè)/共116頁(yè)MergerandInternalizationButwhyisthemergedfirm’spollutionlevelofxm=2efficient?Theexternalcostinflictedonthefisheryisxf,sothemarginalexternalpollutioncostis第84頁(yè)/共116頁(yè)MergerandInternalizationButwhyisthemergedfirm’spollutionlevelofxm=2efficient?Theexternalcostinflictedonthefisheryisxf,sothemarginalexternalpollutioncostisThesteelfirm’scostofreducingpollutionis第85頁(yè)/共116頁(yè)MergerandInternalizationButwhyisthemergedfirm’spollutionlevelofxm=2efficient?Theexternalcostinflictedonthefisheryisxf,sothemarginalexternalpollutioncostisThesteelfirm’scostofreducingpollutionisEfficiencyrequires第86頁(yè)/共116頁(yè)MergerandInternalizationMergerthereforeinternalizesanexternalityandinduceseconomicefficiency.Howelsemightinternalizationbecausedsothatefficiencycanbeachieved?第87頁(yè)/共116頁(yè)CoaseandProductionExternalitiesCoasearguesthattheexternalityexistsbecauseneitherthesteelfirmnorthefisheryownsthewaterbeingpolluted.Supposethepropertyrighttothewateriscreatedandassignedtooneofthefirms.Doesthisinduceefficiency?第88頁(yè)/共116頁(yè)CoaseandProductionExternalitiesSupposethefisheryownsthewater.Thenitcansellpollutionrights,inacompetitivemarket,at$pxeach.Thefishery’sprofitfunctionbecomes

第89頁(yè)/共116頁(yè)CoaseandProductionExternalitiesSupposethefisheryownsthewater.Thenitcansellpollutionrights,inacompetitivemarket,at$pxeach.Thefishery’sprofitfunctionbecomes

Givenpfandpx,howmanyfishandhowmanyrightsdoesthefisherywishtoproduce?(Noticethatxisnowachoicevariableforthefishery.)第90頁(yè)/共116頁(yè)CoaseandProductionExternalitiesTheprofit-maximumconditionsare第91頁(yè)/共116頁(yè)CoaseandProductionExternalitiesTheprofit-maximumconditionsareandthesegive(fishsupply)(pollutionrightsupply)第92頁(yè)/共116頁(yè)CoaseandProductionExternalitiesThesteelfirmmustbuyonerightforeveryunitofpollutionitemitssoitsprofitfunctionbecomes

Givenpfandpx,howmuchsteeldoesthesteelfirmwanttoproduceandhowmanyrightsdoesitwishtobuy?第93頁(yè)/共116頁(yè)CoaseandProductionExternalitiesTheprofit-maximumconditionsare第94頁(yè)/共116頁(yè)CoaseandProductionExternalitiesTheprofit-maximumconditionsareandthesegive(steelsupply)(pollutionrightdemand)第95頁(yè)/共116頁(yè)CoaseandProductionExternalitiesInacompetitivemarketforpollutionrightsthepricepxmustadjusttoclearthemarketso,atequilibrium,第96頁(yè)/共116頁(yè)CoaseandProductionExternalitiesInacompetitivemarketforpollutionrightsthepricepxmustadjusttoclearthemarketso,atequilibrium,Themarket-clearingpriceforpollutionrightsisthus第97頁(yè)/共116頁(yè)CoaseandProductionExternalitiesInacompetitivemarketforpollutionrightsthepricepxmustadjusttoclearthemarketso,atequilibrium,Themarket-clearingpriceforpollutionrightsisthusandtheequilibriumquantityofrightstradedis第98頁(yè)/共116頁(yè)CoaseandProductionExternalities第99頁(yè)/共116頁(yè)CoaseandProductionExternalitiesSoifps=12andpf=10thenThisistheefficientoutcome.第100頁(yè)/共116頁(yè)CoaseandProductionExternalitiesQ:Woulditmatterifthepropertyrighttothewaterhadinsteadbeenassignedtothesteelfirm?A:No.Profitislinear,andthereforequasi-linear,inmoneysoCoase’sTheoremstatesthatthesameefficientallocationisachievedwhicheverofthefirmswasassignedthepropertyright.(Andtheassetownergetsricher.)第101頁(yè)/共116頁(yè)TheTragedyoftheCommonsConsideragrazingareaowned“incommon”byallmembersofavillage.Villagersgrazecowsonthecommon.Whenccowsareg