【導讀】容符合論文要求，達到本科水平。對于對稱的公共池塘資源，我們已經建立了提高效率的“按比例縮減”，但。隨之帶來的各種復雜因素引起了“按比例縮減”閉聯集的不對稱。但很顯然，由于其中自然的?；蝮w制上的障礙，所以其排他性也是非比尋常的，并且收益將會減少。設置數據，它們主要記錄了個體所面對的，很多復雜的，源于CPR設置的占有問題。實驗結果中出現的CPR兩難境地的有限重復結構，從理論上支撐了田野調查的發(fā)現。源使用的平衡預測保持一致。例減少其占有行為。種機制具有非常強的吸引力，因為“按比例縮減”造成了積極的后果。用者的用途不同的事例中，這種機制會導致明顯的分配沖突。的不平衡與效率下降有著密切聯系。在第4部分，一個CPR的變量級模型將推導出，并且進一步。鑒于以上的原因，國際上開始討論并制定限制商業(yè)CFC排放量的條約。這種限令是“按比例縮減”局限性的一個典型事例——100%的縮減。了空調、冰箱的生產成本，其價格也相應提高了。

　　

【正文】 . Not all international attempts to use proportional cutbacks are as successful as the Montreal Protocol. To cite just one example, consider the mon fisheries of the European Union_EU.. Persistent overfishing of EU waters has led to serious declines in the population of species such as cod, herring, mackerel, sole, sardines, and salmon. Fishing at current levels is clearly unsustainable, and could lead to mercial extinction of all the above species in EU waters. Indeed, the problem has been so severe as to lead to international incidents involving EU member countries and other countries _UK vs. Iceland, France vs. Canada, Spain] vs. Canada., as well as tensions between EU members. In an attempt to address the situation, the European Commission in 1996 proposed a proportional cutback of 40% in the fishing fleets of all EU member countries, to be phased in over 6 years. These cutbacks were attacked by various countries, and the Commission withdrew the plan rather than see it vetoed. The discussion exhibited a sharp difference between rich and poor fishing countries — with Spain and Portugal wanting little if any reduction in their fleets, while the UK wanted even larger reductions in Spanish and Portuguese fleets. In April of 1997, the European Commission brought forward a revised proportional cutbacks plan. Under this plan, fishing fleets are to be differentially reduced, depending on the severity of the overfishing. For species in the category ‘‘most endangered,’’ fishing fleets are to be cut back by 30% over the next 5 years. This category includes Atlantic salmon and Atlantic swordfish. For species in the category ‘‘overfished,’’ fleets are to be cut back by 20% over that same period. For all other species, the size of the fishing fleet is frozen. The European Council decided this revised plan by weighted majority rule. France and the UK, both still opposed to the revised plan, were outvoted by the rest of the member states _Pesca, 1998.. It is still too early to tell if the EU’s adoption of a variety of proportional cutbacks, after 40 years of overfishing, will lead to a eback in mercial fish populations. In this regard, the experience of Canada, which used similar cutbacks in an attempt to save its ‘‘most endangered’’ cod fishery, is hardly cause for optimism. The Canadian cod fishery, despite 25 years of fisheries policy that attempted to sustain it, is now mercially extinct_Finlayson and McCay, 1998.. The difficulties facing the EU are even greater, given the international dimension. Consider the most endangered Atlantic swordfish. The current international agreement calls for only 11,300 tons to be taken in a given year — a rough estimate of sustainable use. By contrast, the actual harvest is 16,000 tonsryear — half of which is taken by EU members. Proportional cutbacks on the part of all countries involved in this fishery_USA, Canada, Japan, EFTA roughly 30% are called for to restore the agreed level. Even if the EU were to cut its harvest back by 30%, from 8000 to 5600 tons, that would still only go halfway to solving the Atlantic swordfish problem. These cases illustrate situations in which resource users have adopted proportional cutback institutions in an attempt to reduce overall appropriation levels. The theoretical results of the next two sections examine the extent to which such a simple institution as proportional cutbacks can lead to desirable efficiency and distributional consequences.