曼昆经济学 宏观经济学 第五版 教师参考手册 chap10.docx
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曼昆经济学 宏观经济学 第五版 教师参考手册 chap10.docx
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曼昆经济学宏观经济学第五版教师参考手册chap10
100
EXTERNALITIES
WHAT’SNEW:
Thedefinitionofexternalityhasbeenimproved.AnewCaseStudy“WhyisGasolineTaxedSoHeavily?
”hasbeenadded.ThereisalsoanewIntheNewsboxon“ChildrenasExternalities.”
LEARNINGOBJECTIVES:
Bytheendofthischapter,studentsshouldunderstand:
Øwhatanexternalityis.
Øwhyexternalitiescanmakemarketoutcomesinefficient.
Øhowpeoplecansometimessolvetheproblemofexternalitiesontheirown.
Øwhyprivatesolutionstoexternalitiessometimesdonotwork.
Øthevariousgovernmentpoliciesaimedatsolvingtheproblemofexternalities.
KEYPOINTS:
1.Whenatransactionbetweenabuyerandsellerdirectlyaffectsathirdparty,thateffectiscalledanexternality.Negativeexternalities,suchaspollution,causethesociallyoptimalquantityinamarkettobelessthantheequilibriumquantity.Positiveexternalities,suchastechnologyspillovers,causethesociallyoptimalquantitytobegreaterthantheequilibriumquantity.
2.Thoseaffectedbyexternalitiescansometimessolvetheproblemprivately.Forinstance,whenonebusinessconfersanexternalityonanotherbusiness,thetwobusinessescaninternalizetheexternalitybymerging.Alternatively,theinterestedpartiescansolvetheproblembysigningacontract.AccordingtotheCoasetheorem,ifpeoplecanbargainwithoutcost,thentheycanalwaysreachanagreementinwhichresourcesareallocatedefficiently.Inmanycases,however,reachingabargainamongthemanyinterestedpartiesisdifficult,sotheCoasetheoremdoesnotapply.
3.Whenprivatepartiescannotadequatelydealwithexternaleffects,suchaspollution,thegovernmentoftenstepsin.Sometimesthegovernmentpreventssociallyinefficientactivitybyregulatingbehavior.OthertimesitinternalizesanexternalityusingPigouviantaxes.Anotherwaytoprotecttheenvironmentisforthegovernmenttoissuealimitednumberofpollutionpermits.TheendresultofthispolicyislargelythesameasimposingPigouviantaxesonpolluters.
CHAPTEROUTLINE:
I.DefinitionofExternality:
theuncompensatedimpactofoneperson’sactionsonthewell-beingofabystander.
A.Iftheeffectonthebystanderisadverse,wesaythatthereisanegativeexternality.
B.Iftheeffectonthebystanderisbeneficial,wesaythatthereisapositiveexternality.
Givestudentsseveralexamplesofbothpositiveandnegativeexternalities.Usecurrenthealthdebatesorpoliticaltopicstomaintaininterest.
C.Ineithersituation,decisionmakersfailtotakeaccountoftheexternaleffectsoftheirbehavior.
II.ExternalitiesandMarketInefficiency
Figure10-1
A.WelfareEconomics:
ARecap
1.Thedemandcurveforaproductreflectsthevalueofthatproducttoconsumers,measuredbythepricethatbuyersarewillingtopay.
2.Thesupplycurveforaproductreflectsthecostofproducingtheproduct.
3.Inafreemarket,thepriceofagoodbringssupplyanddemandintobalanceinawaythatmaximizestotalsurplus(thedifferencebetweentheconsumers’valuationofthegoodandthesellers’costofproducingit).
B.NegativeExternalitiesinProduction
Figure10-2
ALTERNATIVECLASSROOMEXAMPLE:
Acoal-firedpowerplant.
1.Example:
analuminumfirmemitspollutionduringproduction.
2.Socialcostisequaltothecosttothefirmofproducingthealuminumplustheexternalcoststothosebystandersaffectedbythepollution.Thus,socialcostexceedstheprivatecostpaidbyproducers.
3.Theoptimalamountofaluminuminthemarketwilloccurwheretotalsurplusismaximized.
a.Totalsurplusisequaltothevalueofaluminumtoconsumersminusthecost(socialcost)ofproducingit.
b.Thiswilloccurwherethesocialcostcurveintersectswithdemandcurve.Atthispoint,producingonemoreunitwouldlowertotalsurplusbecausethevaluetoconsumersislessthanthecosttoproduceit.
SocialCost
Supply(privatecost)
Price
Demand
(privatevalue)
Qmarket
Qoptimum
Quantity
4.Becausethesupplycurvedoesnotreflectthetruecostofproducingaluminum,themarketwillproducemorealuminumthanisoptimal.
Makesurethatstudentsunderstandhowthispollutionbythefirmimposescostsonthirdparties.Pointoutthatthefirmislikelyemittingpollutionbecausethisisthecheapestmethodofproduction.Stressthatthefirmisusingaresourceinproductionthatitisnotpayingfor.
5.Thisnegativeexternalitycouldbeinternalizedbyataxonproducersforeachunitofaluminumsold.
6.DefinitionofInternalizinganExternality:
alteringincentivessothatpeopletakeaccountoftheexternaleffectsoftheiractions.
C.PositiveExternalitiesinProduction
Figure10-3
1.Example:
technologyspilloverintheproductionofindustrialrobots.
2.Inthiscase,socialcostistheprivatecostminusthevalueofthetechnologyspillover.Therefore,socialcostissmallerthantheprivatecost.
Supply(privatecost)
Price
SocialCost
Demand
(privatevalue)
Qmarket
Qoptimum
Quantity
3.Theoptimalamountofindustrialrobotsinthemarketwilloccurwheretotalsurplusismaximized(wheresocialcostintersectswiththedemandcurve).
4.Becausethesupplycurvedoesnotreflectthetruecostofproducingrobots(whichislowerthantheprivatecost),themarketwillproducefewerrobotsthanisoptimal.
5.Theexternalitycanbeinternalizedthroughasubsidyfromthegovernmentforeachrobotproduced.
6.CaseStudy:
TheDebateOverTechnologyPolicy
a.Itisdifficulttomeasuretheamountsoftechnologyspilloverthatoccurandthisleadstoadebateoverwhetherornotthegovernmentshouldpursuepoliciestoencouragetheproductionoftechnology.
b.Patentprotectionisatypeoftechnologypolicyofthegovernmentbecauseitprotectstherightsofinventorswhocreatenewtechnologies.Withoutpatents,therewouldbelessincentivetodevelopnewideasandtechnologies.
D.ExternalitiesinConsumption
Figure10-4
1.Whenthereareexternalitiesinconsumption,thedemandcurvedoesnotreflectthesocialvalueofagood.
Thisisagoodtimetodiscusswhythegovernmenttaxesgoodslikealcohol,tobacco,andgasoline.Youwillfindthatstudentshaveheardthephrase“sintax”,buttheyoftendonotunderstandwhyeconomistsmightsupportsuchtaxes(giventhedeadweightlossfromtaxesdiscussedinChapter8).
Supply(privatecost)
Price
Demand
(privatevalue)
Social
Value
Qmarket
Qoptimum
Quantity
ALTERNATIVECLASSROOMEXAMPLE:
Thepurchaseofafireextinguisherwhenanindividuallivesinanapartment.
a.Ifthereisanegativeexternalityinconsumption,thesocialvalueofthegoodislessthantheprivatevalue,andtheoptimumquantitywillbelowerthanthequantityproducedinthemarket.
b.Ifthereisapositiveexternalityinconsumption,thesocialvalueofthegoodisgreaterthantheprivatevalue,andtheoptimumquantitywillbegreaterthanthequantityproducedinthemarket.
2.Tointernalizeanegativeexternalityinconsumption,thegovernmentcouldagainuseatax;tointernalizeapositiveexternality,itcoulduseasubsidy.
Supply(privatecost)
Price
Social
Value
Demand
(privatevalue)
Qoptimum
Qmarket
Quantity
III.PrivateSolutionstoExternalities
A.Wedonotnecessarilyneedgovernmentinvolvementtocorrectexternalities.
B.TheTypesofPrivateSolutions
1.Problemsofexternalitiescansometimesbesolvedbymoralcodesandsocialsanctions.
2.Manycharitieshavebeenestablishedthatdealwithexternalities.
3.Thepartiesinvolvedinthisexternality(eitherthesellerandthebystanderortheconsumerandthebystander)canpossiblyenterintoanagreementtocorrecttheexternality.
C.TheCoaseTheorem
1.DefinitionofCoaseTheorem:
thepropositionthatifprivatepartiescanbargainwithoutcostovertheallocationofresources,theycansolvetheproblemofexternalitiesontheirown.
2.Example:
Dickownsadogthatdisturbsaneighbor(Jane)withitsbarking.
a.OnepossiblesolutiontothisproblemwouldbeforJanetopayDicktogetridofthedog.Theamountthatshewouldbewillingtopaywouldbeequaltohervaluationofthecostsofthebarking.DickwouldonlyagreetothisifJanepaidhimanamountgreaterthanthevalueheplacesonowningSpot.
b.EvenifJanecouldlegallyforceDicktogetridofSpot,anothersolutioncouldoccur.DickcouldpayJanetolethimkeepthedog.
3.Thepartiesinvolvedinanexternalitycansolvetheproblemthemselvesandreachanefficientoutcomewherebothpartiesarebetteroff.
D.WhyPrivateSolutionsDoNotAlwaysWork
1.DefinitionofTransactionCosts:
thecoststhatpartiesincurintheprocessofagreeingandfollowingthroughonabargain.
2.Coordinationofalloftheinterestedpartiesmaybedifficultsothatbargainingbreaksdown.
IV.PublicPoliciestowardExternalities
A.Regulation
1.Externalitiescanbecorrectedbymakingcertainbehaviorseitherrequiredorforbidden.
2.IntheUnitedStates,itistheEnvironmentalProtectionAgency(EPA)thatdevelopsandenforcesregulationsaimedatprotectingtheenvironment.
3.EPAregulationsincludemaximumlevelsofpollutionallowedorrequiredadoptionofaparticulartechnologytoreduceemissions.
B.PigovianTaxesandSubsidies
1.Externalitiescanbeinternalizedthroughtheuseoftaxesandsubsidies.
2.DefinitionofPigouvianTax:
ataxenactedtocorrecttheeffectsofanegativeexternality.
a.Thesetaxesarepreferredbyeconomistsoverregulation,becausefirmswhichcanreducepollutionwiththeleastcostarelikelytodoso(toavoidthetax)whilefirmsthatencounterhighcostswhenreducingpollutionwillsimplypay
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