经济学（微观）（英文版原书第7版）课件 第5章　外部性、环境政策和公共产品

EconomicsSeventhEditionChapter5Externalities,EnvironmentalPolicy,andPublicGoodsCopyright©2019,2017,2015PearsonEducation,Inc.AllRightsReserved.ExxonMobilWantstoPayaCarbonTax?In2017,ExxonMobil’sCEOconfirmedsupportfora“carbontax”,ataxbasedonthecarboncontentofenergyproduction.Why?Notbecausehewantedtopaymoretax!Butbecausehebelievedatax—amarket-basedpolicy—wouldbeabetterwaytodealwithpollutioninthelongrunthanthecurrentpatchworkofcommand-and-controlpolicies.BothforExxonMobil,andforsociety.ChapterOutline5.1

ExternalitiesandEconomicEfficiency5.2

PrivateSolutionstoExternalities:TheCoaseTheorem5.3

GovernmentPoliciestoDealwithExternalities5.4

FourCategoriesofGoods5.1ExternalitiesandEconomicEfficiencyIdentifyexamplesofpositiveandnegativeexternalitiesandusegraphstoshowhowexternalitiesaffecteconomicefficiency.Noonesetsouttocreatepollution;pollutionisanunintendedby-productofvariousactivities.Pollutionwouldnotbeaproblemifpollutiononlyaffectedthepersonwhocreatedit;peoplewouldcreatepollutiononlyuntilitsmarginalcostequaleditsmarginalbenefit.Butpollutionisanexampleofanexternality:abenefitorcostthataffectssomeonewhoisnotdirectlyinvolvedintheproductionorconsumptionofagoodorservice.Thinkofanexternalitylikeaside-effect.EnergyProductionEnergyproductionisanincrediblyimportantindustryforamoderneconomy.Considerthemarketforelectricity.Itconsistsof:Sellers,whofaceincreasingmarginalcoststoproduceelectricityBuyers,whofacedecreasingmarginalbenefitsofadditionalelectricityTheactionsofthesegroupsgeneratemarketsupplyanddemandcurvesforelectricity.CostofElectricityProductionWhenfirmsproduceelectricity,theybearcertaincostsofproduction:BuildingsEquipmentFuelLabor,etc.Thosefirmsmaketheirdecisionsabouthowmuchtoproducebasedontheseprivatecosts.Butbecauseofpollutionthesocialcost

ishigher:thetotalcosttosocietyofproducingagoodorservice,includingboththeprivatecostandanyexternalcost.Figure5.1TheEffectofPollutiononEconomicEfficiency(1of3)SupplycurveS1representsjustthemarginalprivatecostthattheelectricityproducerhastopay.SupplycurveS2representsthemarginalsocialcost,whichincludesthecoststothoseaffectedbypollution.TheoptimallevelofproductionforsocietyisQEfficient;atthisquantity,themarginalcosttosocietyisjustequaltothemarginalbenefit.Figure5.1TheEffectofPollutiononEconomicEfficiency(2of3)Howeverthemarketequilibriumresultsfromthedecisionsofproducers,whoseetheircostofproductiongivenbyS1.Price(PMarket)is“toolow”andquantity(QMarket)is“toohigh”:thecosttosocietyoftheadditionalelectricityexceedsitsbenefittosociety.Deadweightlossresults.Figure5.1TheEffectofPollutiononEconomicEfficiency(3of3)Whenthereisanegativeexternalityinproducingorconsumingagoodorservice,toomuchofthegoodorservicewillbeproducedatmarketequilibrium.TypesofExternalitiesPollutionisanexampleofanegativeexternalityinproduction.Negativeexternalitiesmightresultfromconsumption.Example:cigarettesmoke.Externalitiesmightalsobepositivewhentheprivatebenefit(thebenefitreceivedbytheconsumerofagoodorservice)islessthanthesocialbenefit(thetotalbenefitfromconsumingagoodorservice,includingboththeprivatebenefitandanyexternalbenefit).Example:collegeeducationFigure5.2TheEffectofaPositiveExternalityonEconomicEfficiency(1of2)Collegeeducationshavepositiveexternalities.Themarginalsocialbenefitfromacollegeeducationisgreaterthanthemarginalprivatebenefittocollegestudents.BecauseonlythemarginalprivatebenefitisrepresentedinthemarketdemandcurveD1,thequantityofcollegeeducationsproduced,QMarket,istoolow.Figure5.2TheEffectofaPositiveExternalityonEconomicEfficiency(2of2)Whenthereisapositiveexternalityinproducingorconsumingagoodorservice,toolittleofthegoodorservicewillbeproducedatmarketequilibrium.ExternalitiesandMarketFailureIftherearenegativeorpositiveexternalities,themarketequilibriumwillnotresultintheefficientquantitybeingproduced.Overproductionwithnegativeexternalities;underproductionwithpositiveexternalities.Therewillbedeadweightloss.Thisisanexampleofmarketfailure:asituationinwhichthemarketfailstoproducetheefficientlevelofoutput.Thelargertheexternality,thegreaterislikelytobethesizeofthedeadweightloss—theextentofthemarketfailure.5.2PrivateSolutionstoExternalities:TheCoaseTheoremDiscusstheCoasetheoremandexplainhowprivatebargainingcanleadtoeconomicefficiencyinamarketwithanexternality.Externalitiesarisebecauseofincompletepropertyrights,orfromthedifficultyofenforcingpropertyrightsincertainsituations.Propertyrights:Therightsindividualsorbusinesseshavetotheexclusiveuseoftheirproperty,includingtherighttobuyorsellit.Here“property”canbetangibleorphysical,suchasafactoryoranaturalresource;orintangible,suchasinventions—intellectualproperty.PropertyRightsCanSolvetheExternalityProblemSupposeafarmerandapapermillshareastream.Ifnooneownsthestream,thepapermillwilldischargewasteintothestream,makingitunusableforthefarmer.Ifthefarmerownsthestream,hecan:Preventthemillfromdischargingintothestream,orAllowthemilltodischargeforafee,ifthatismorebeneficialtohim.Eitherway,goodpropertyrightsavoidthemarketfailure.Is“ZeroPollution”Efficient?Thepreviousslidesuggestedthatavoidingpollutionaltogetheristhebestsolution.Butwhatifthepapermillsavesalotofmoneybydischargingintothestream,andthefarmerhasanalternativewatersupply?Muchofthetime,anon-zeroamountofpollutionisoptimal,determinedbywherethemarginalbenefitfrompollutionisjustequaltothemarginalcostofpollution.Orequivalently,themarginalcostofpollutionreductionequalsthemarginalbenefitfrompollutionreduction.Figure5.3TheMarginalBenefitfromPollutionReductionShouldEqualtheMarginalCostThisgraphshowspollutionreduction,whichhasbothcostsandbenefits.7unitsofpollutionreductionis“toolittle”;thebenefitofthenextunitexceedsthecost.10unitsofpollutionreductionis“toomuch”;thecostofthelastunitexceedsthebenefit.8.5unitsisefficient;themarginalcostjustequalsthemarginalbenefit.ApplytheConcept:TheCleanAirActandInfantMortalityPresidentNixonsignedintolawtheCleanAirActin1970;by2017,totalemissionsofthesixmainairpollutantshadfallenbyatleast50%each.Withhigherpollutionlevelsin1970,thebenefitsofpollutionproductionmusthavebeenveryhigh.Severalstudiesidentifylargebenefitsfromthereductioninpollution,comparedwithwhatwouldhavehappenedwithoutthelaw:In1972,1,300fewerinfantsand9,900fewerfetusesdied.Healthierchildrenborninthepreviouslymostpollutedcountiesearned~$4,300moreasadults.Figure5.4TheBenefitsofReducingPollutiontotheOptimalLevelAreGreaterThantheCosts(1of2)Increasingthereductioninsulfurdioxideemissionsfrom7.0milliontonsto8.5milliontonsresultsintotalbenefitsequaltothesumoftheareasAandBunderthemarginalbenefitscurve.ThetotalcostofthisdecreaseinpollutionisequaltotheareaBunderthemarginalcostcurve.ThetotalbenefitsaregreaterthanthetotalcostsbyanamountequaltotheareaoftriangleA.Figure5.4TheBenefitsofReducingPollutiontotheOptimalLevelAreGreaterThantheCosts(2of2)Inprinciple,privatepartiescouldachievetheefficientlevelofpollution.Peoplefeelingthecostoftheadditionalpollution(A+B)couldpaypollutersanamountequaltoB;thenpolluterswouldchoosenottopollute.Butifthebenefitsofpollutionreductionarefeltdiffusely(bymanywidespreadpeople),achievingthisoutcomeisdifficult—wesaythetransactionscostsaretoohigh.TheCoaseTheoremNobellaureateRonaldCoasearguedthatprivatepartiescouldsolvetheexternalityproblemthroughprivatebargaining,provided:Propertyrightsareassignedandenforceable,andTransactionscostsarelow.ThisideahascometobeknownastheCoasetheorem.Transactionscosts:Thecostsintimeandotherresourcesthatpartiesincurintheprocessofagreeingtoandcarryingoutanexchangeofgoodsorservices.TheCoasetheoremalsorequiresthatpartieshavefullinformationaboutthecostsandbenefitsinvolved.TheCoaseTheoremandPropertyRightsPerhapsCoase’smostimportantobservationwasthatitdidnotmattertowhompropertyrightswereassigned.Intheexampleofthepapermillandthefarmer,wesaidthatifthefarmerhadenforceablepropertyrightsoverthestream,theexternalityproblemcouldberesolved.Butthesameistrueifthepapermillownsthestream!Canyouexplainwhy?ApplytheConcept:DefendingYourKneesonaPlaneFlightDoesthepersonsittinginfrontofyouhavetherighttoreclinetheirseat?Theanswerseemstobeyes.NYTcolumnistJoshBarrosuggeststheCoasetheoremallowsforasolution:paythepersoninfrontofyoutonotreclinetheirseat.DoyouthinktransactionscostsaresmallenoughherefortheCoasetheoremtoapply?5.3GovernmentPoliciestoDealwithExternalitiesAnalyzegovernmentpoliciestoachieveeconomicefficiencyinamarketwithanexternality.Inchapter4,welearnedthattaxescausedinefficiency(deadweightloss)bymovingthelevelofproductionawayfromtheefficientlevel.Inthischapter,externalitiescauseinefficiencyforthesamereason.Ataxofjusttherightsizecouldcausethesetwoeffectstocancelout,returningustotheefficientlevelofproduction.Figure5.5WhenThereisaNegativeExternality,aTaxCanLeadtotheEfficientLevelofOutput(1of2)Utilitiesdonotbearthecostofpollution,sotheyproducetoomuch.Ifthegovernmentimposesataxequaltothecostofthepollution,theutilitieswillinternalizetheexternality.Thesupplycurvewillshiftup,fromS1toS2.Themarketequilibriumquantityfallstotheeconomicallyefficientlevel.Figure5.5WhenThereisaNegativeExternality,aTaxCanLeadtotheEfficientLevelofOutput(2of2)ThepriceofelectricitywillrisefromPMarket,whichdoesnotincludethecostofacidrain,toPEfficient,whichdoesincludethecost.ConsumerspaythepricePEfficient,whileproducersreceiveapriceP,whichisequaltoPEfficientminustheamountofthetax.CanTaxes“Solve”PositiveExternalitiesToo?Taxesworkedtosolvetheproblemofnegativeexternalitiesbecause:Negativeexternalitiescausedtoomuchtobeproduced,whileTaxesreducedtheamountofoutput.Whentherearepositiveexternalities,toolittlewillbeproduced.Taxeswon’twork;butsubsidiesmight:amountspaidtoproducersorconsumerstoencouragetheproductionorconsumptionofagood.Figure5.6WhenThereisaPositiveExternality,aSubsidyCanBringabouttheEfficientLevelofOutput(1of2)Individualsmakedecisionsaboutwhetherornotto“consume”acollegeeducation,witharesultingmarketpriceandquantity.Butwhatiftherearepositiveexternalitiestoacollegeeducation?Itisgoodforusallifotherpeoplearesmartandmakegooddecisions.Thisisanargumentforasubsidyinthemarketforcollegeeducation.Figure5.6WhenThereisaPositiveExternality,aSubsidyCanBringabouttheEfficientLevelofOutput(2of2)Thesubsidywillcausethedemandcurvetoshiftup,fromD1toD2.ThemarketequilibriumquantitywillshiftfromQMarkettoQEfficient,theeconomicallyefficientequilibriumquantity.ProducersreceivethepricePEfficient,whileconsumerspayapriceP,whichisequaltoPEfficientminustheamountofthesubsidy.CorrectiveTaxesandSubsidiesThetaxesandsubsidiesseeninthelastfewslides“correct”theexternalityproblem.TheyareknownasPigoviantaxesandsubsidies,aftertheEnglisheconomistArthurCecilPigou,whofirstdemonstratedtheuseofgovernmenttaxesandsubsidiesinbringingaboutanefficientlevelofoutputinthepresenceofexternalities.Pigoviantaxesareespeciallypopularwitheconomists,becausetheyincreaseefficiencywhilebringingintaxrevenue;then(intheory)thisallowsinefficiency-causingtaxesinothermarketstobereduced,adoubledividendoftaxation.ApplytheConcept:ShouldWeTaxCigarettesandSoda?(1of2)Theconsumptionofcigarettesandsodaarethoughttohavenegativeexternalities.Why?Bothcigarettesandsodahavenegativehealthconsequences.Thisbyitselfisnotsufficienttobeanegativeexternality.Butpeople’smedicalexpensesaresharedwithothers,eitherviapublicorprivatehealthinsurance.Thereforeweexpecttheretobetoomuchconsumptionofcigarettesandsoda,andtheyarecandidatesforPigoviantaxes.Ingeneral,cigarettesaretaxedmuchmoreheavilythansoda.Isthisappropriate?ApplytheConcept:ShouldWeTaxCigarettesandSoda?(2of2)AlternativestoTaxationforSolvingExternalitiesThetraditionalsolutiontotheexternalityproblemisthecommand-and-controlapproach:apolicythatinvolvesthegovernmentimposingquantitativelimitsontheamountofpollutionfirmsareallowedtoemit,orrequiringfirmstoinstallspecificpollutioncontroldevices.Example:Requiringcarmanufacturerstoequipcarswithcatalyticconverters.Problem:Whatiffirmshaveverydifferentcostsofreducingpollution?Itmaynotbeefficientforthemtoreducepollutionbythesameamount.i.e.thesameamountofpollution-reductioncouldbeachievedwithlesscostTwoCarManufacturersSupposeFordcanreducepollutioninitscarsverycheaply,whileGMhasveryhighcostsofreducingpollution.Ifwewanttoachieveaparticularlevelofpollutionreduction,itwouldbeefficienttoaskFordtoreducepollutionmorethanGM.Butthisdoesn’tseemfairtoFord;whyshouldGMbeheldtoalesserstandard?TheefficientsolutionhasFordperformmorepollutionreduction,buthaveGMcompensateFord;bothcompaniescanbemadebetteroff,comparedwithrequiringbothtoreducepollutionbyamoderateamount,whilekeepingtheamountofpollutionreductionthesame.TradableEmissionsPermitsThisistheconceptbehindtradableemissionspermits,alsoknownascap-and-trade:Thegovernmentestablishesanallowableamountofemissions.Emissionspermitsaredistributed.Firmscantradeemissionspermits.Firmswithhighcostsofreducingpollutionwillbuypermitsfromfirmswithlowcostsofreducingpollution,ensuringthatpollutionisreducedatthelowestpossiblecost.Hencethemarketisusedtoachieveefficientpollutionreduction.TheSulfurDioxideCap-and-TradeSystemIn1990,Congressenactedacap-and-tradesystemforsulfurdioxideemissions.Improvementsinpollutionreductiontechnologyresulted,withthecostofcomplianceendingupalmost90percentlessthanfirminitiallyestimated.Thisprogramwasveryeffective,withbenefitsatleast25timesthecostofimplementingtheprogram.TheEndoftheSulfurDioxideCap-and-TradeSystemBy2013,theprogramhadeffectivelyended.Why?Furtheremissionsreductionswereneeded;PresidentBushattemptedtolowerthecap,butCongressresisted.Asaresult,theEPAdecidedtoreturntoacommand-and-controlapproachinordertoachievethereductions.Whilecap-and-tradeappearstobeveryeffective,anypolicyneedspoliticalbackingtohaveachanceatsuccess.CriticismsofCap-and-TradeEnvironmentalistsobjecttocap-and-tradeasitgivesfirms“licensestopollute.”Butpollutionhasabenefit;itallowscheapproduction.Everyproductiondecisionusesupsomescarceresource:time,naturalresources,cleanair,etc.Inthissense,payingforusingthecleanairseemsappropriate.Amoreseriousconcernisthatcap-and-trademayproducehot-spots,locationswherealotofpollutiontakesplace.Thiswouldbethecaseifthefirmswithhighcostsofpollutionreductionweregeographicallyclose.Doyouthinkthisislikely?WhyHasCap-and-TradeLostItsPopularity?Cap-and-tradealterswhopaysforpollution:Whenpollutionisunregulated,allconsumersbeartheconsequencesofpollution.Whencap-and-tradeisenacted,thecostofpollutionisbornedirectlybyfirms.Pollutingfirmstendtobeabletoorganizebetterlobbyingefforts,becauseconsumersfeelthecostofpollutiondiffusely.Thisillustratestheclassicspecial-interestprobleminpolitics:smallgroupsarebetterabletoorganizethanlargegroups,evenwhenthelargegroupsmightbenefitalotfromorganizing.5.4FourCategoriesofGoodsCategorizegoodsonthebasisofwhethertheyarerivalorexcludableandusegraphstoillustratetheefficientquantitiesofpublicgoodsandcommonresources.Wehaveseenthatmarketsarebetteratprovidingtheefficientlevelofsomegoodsandservicesthanothers.Thisisrelatedtosomeimportantattributesofthegoodsandservices:whethertheirconsumptionisrivaland/orexcludable.Rivalry:Thesituationthatoccurswhenoneperson’sconsumingaunitofagoodmeansnooneelsecanconsumeit.Excludability:Thesituationinwhichanyonewhodoesnotpayforagoodcannotconsumeit.Figure5.7FourCategoriesofGoodsEfficientProvisionoftheCategoriesofGoodsMarketstendtobegoodatprovidingefficientlevelsofprivategoods.Why?Thepersonmakingdecisionsabouthowmuchtopurchasetendstobetheonlyonebenefitingfromthegood,soonlytheirpreferencesmatter.Marketsarenotsogoodatprovidingefficientlevelsoftheothertypesofgoods.Why?Peoplecanfreerideonpublicgoods,enjoyingthebenefitsfromthemwithoutpayingforthem.Peoplehavelittleincentivetoconservecommonresources,leadingthemtobeoverconsumed.Profit-maximizationtendstoleadtoomanypeopletobeexcludedfromquasi-publicgoods.Figure5.8ConstructingtheMarketDemandCurveforaPrivateGoodThemarketdemandcurveforprivategoodsisdeterminedbyaddinghorizontallythequantityofthegooddemandedateachpricebyeachconsumer.Inpanel(a),Jilldemands2hamburgerswhenthepriceis$4.00,andinpanel(b),Joedemands4hamburgerswhenthepriceis$4.00.Aquantityof2+4=6hamburgersandapriceof$4.00isapointonthemarketdemandcurveinpanel(c).Figure5.9ConstructingtheDemandCurveforaPublicGoodTofindthedemandcurveforapublicgood,weaddupthepriceatwhicheachconsumeriswillingtopurchaseeachquantityofthegood.Inpanel(a),Jilliswillingtopay$8perhourforasecurityguardtoprovide10hoursofprotection.Inpanel(b),Joeiswillingtopay$10forthatlevelofprotection.Therefore,inpanel(c),thepriceof$18perhourandthequantityof10hourswillbeapointonthedemandcurveforsecurityguardservices.Figure5.10TheOptimalQuantityofaPublicGoodInprinciple,determiningtheefficientlevelofproductionofapublicgoodisthesameasforaprivategood:itiswherethedemandandsupplycurvesintersect.Butfindingthismarketdemandcurvecanbedifficult;consumersmaynothaveincentivestorevealtheirwillingnesstopayforpublicgoods.Cost-benefitanalysiscanbeusefultodeterminethecorrectlevelsofpublicgoods.EfficientConsumptiono