過(guò)度捕撈的外部性過(guò)度捕撈存在外部性原因2.外部性在過(guò)度捕撈中發(fā)揮的作用Anexternalityreferstotheuncompensatedimpactofoneperson’sactionsonthewell-beingofabystander.Externalitiescausemarketstobeinefficient,andthusfailtomaximizetotalsurplus. ...whenapersonengagesinanactivitythatinfluencesthewell-beingofabystanderandyetneitherpaysnorreceivesanycompensationforthateffect.…當(dāng)一個(gè)人的行為影響到旁觀者的福利時(shí)，若此人既不為此支付成本（給旁觀者帶來(lái)成本時(shí)）又不能得到補(bǔ)償（給旁觀者帶來(lái)利益時(shí)），外部性就產(chǎn)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(guó)政府的解決之路1.為防止過(guò)度捕魚，中國(guó)政府要求，2009年5月16日至8月1日期間禁止在我國(guó)南海的部分區(qū)域捕魚，并派出漁政船形成編隊(duì)巡航2.敦促管理者制定更嚴(yán)格的環(huán)境保護(hù)規(guī)定3.中國(guó)政府發(fā)放捕魚證來(lái)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(nèi)在化——通過(guò)增加成本，使人們考慮他們自己過(guò)度捕魚行為的不良效應(yīng)。Thegovernmentcaninternalizeanexternalitybyimposingataxontheproducertoreducetheequilibriumquantitytothesociallydesirablequantity.政府可以向生產(chǎn)者收稅以降低市場(chǎng)均衡產(chǎn)量為社會(huì)所希望的產(chǎn)量，將外部性內(nèi)在化。Indirecttaxation可以被轉(zhuǎn)移的間接稅sellerscansellinahigherprice（Directtaxation針對(duì)個(gè)人收入等

直接稅）科斯定理

TheCoaseTheoremisapropositionthatifprivatepartiescanbargainwithoutcostovertheallocationofresources,theycansolvetheproblemofexternalitiesontheirown.

TypesofPrivateSolutionstoExternalities

Moralcodesandsocialsanctions

道德規(guī)范和社會(huì)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(jìng)爭(zhēng)市場(chǎng)）Tradablepollutionpermits

allowthe

voluntarytransferoftherighttocatchfishfromonefirmtoanother.

Amarketforthesepermitswilleventuallydevelop.Afirmthatcanreduceoutputatalowcostmayprefertosellitspermittoafirmthatcanreduceoutputonlyatahighcost可交易的捕魚證允許捕魚權(quán)交易這種許可證的市場(chǎng)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(méi)有增加，但捕魚證這一稀缺資源重新配置給對(duì)其評(píng)價(jià)更高的企業(yè)。NobodyisgoingtoobeyThemarketiscruel，lowcostforenteringTax