微觀經濟學外部性的講解

過度捕撈的外部性過度捕撈存在外部性原因2.外部性在過度捕撈中發(fā)揮的作用Anexternalityreferstotheuncompensatedimpactofoneperson’sactionsonthewell-beingofabystander.Externalitiescausemarketstobeinefficient,andthusfailtomaximizetotalsurplus. ...whenapersonengagesinanactivitythatinfluencesthewell-beingofabystanderandyetneitherpaysnorreceivesanycompensationforthateffect.…當一個人的行為影響到旁觀者的福利時，若此人既不為此支付成本（給旁觀者帶來成本時）又不能得到補償（給旁觀者帶來利益時），外部性就產生了。Whytheexternalitiesoccur?1.Themostfundamentalreasonisthatresourcesarescarce.2.Becausefishofpublicpondsarecompetitiveandnon-exclusivecommonresources.Itmeansthatapersoncatchesmorefish,leavingotherpeoplelessfishtocatch.What'smore,thepondispublic,fisharenotexclusiveitems,andeveryonecangofishing.So,whenthepondstherearepublicresources,theymaycausetheoverfishing.Thisisagoodnewsforthoseself-interestindividualschasingeachinterestmaximization,butmaycauseharmontheoverall.Profitmaximizingfishingtendstooverfishingandwilldestroylivingsofthecommercialvalueinthepond.3.Andatoolargerangeofresourcesislikelytoleadtothisphenomenon.Overfishingintheinternationalseasisoneexample,leadstoasignificantreductioninfisheriesresourcesandeventothebrinkofextinction.Howtodealwiththis？中國政府的解決之路1.為防止過度捕魚，中國政府要求，2009年5月16日至8月1日期間禁止在我國南海的部分區(qū)域捕魚，并派出漁政船形成編隊巡航2.敦促管理者制定更嚴格的環(huán)境保護規(guī)定3.中國政府發(fā)放捕魚證來保證捕魚量政府稅收（tax）

管制（governmentforce）

捕魚證（marketpower）

道德規(guī)范，協(xié)議合同（CoaseTheorem）PigoviantaxesInternalizinganexternalityinvolvesalteringincentivessothatpeopletakeintoaccounttheexternaleffectsoftheiractions.外部性的內在化——通過增加成本，使人們考慮他們自己過度捕魚行為的不良效應。Thegovernmentcaninternalizeanexternalitybyimposingataxontheproducertoreducetheequilibriumquantitytothesociallydesirablequantity.政府可以向生產者收稅以降低市場均衡產量為社會所希望的產量，將外部性內在化。Indirecttaxation可以被轉移的間接稅sellerscansellinahigherprice（Directtaxation針對個人收入等

直接稅）科斯定理

TheCoaseTheoremisapropositionthatifprivatepartiescanbargainwithoutcostovertheallocationofresources,theycansolvetheproblemofexternalitiesontheirown.

TypesofPrivateSolutionstoExternalities

Moralcodesandsocialsanctions

道德規(guī)范和社會約束Charitableorganizations

慈善組織Integratingdifferenttypesofbusinesses

不同類型的企業(yè)一體化Contractingbetweenparties

交易各方簽訂合同Themarketistoocruel（完全競爭市場）Tradablepollutionpermits

allowthe

voluntarytransferoftherighttocatchfishfromonefirmtoanother.

Amarketforthesepermitswilleventuallydevelop.Afirmthatcanreduceoutputatalowcostmayprefertosellitspermittoafirmthatcanreduceoutputonlyatahighcost可交易的捕魚證允許捕魚權交易這種許可證的市場將最終形成。以低成本可以捕魚的企業(yè)愿意將證出賣給只有以高成本才能捕魚的企業(yè)。捕魚量沒有增加，但捕魚證這一稀缺資源重新配置給對其評價更高的企業(yè)。NobodyisgoingtoobeyThemarketiscruel，lowcostforenteringTax