本文旨在研究存在污染的混合寡占市場下，廠商的生產與污染防治決策會有 何不同，政府又該如何制訂污染稅決策。本文發現在混合雙占市場中，政府課徵 的污染稅越高，民營廠商會減產、公營廠商會增產。而邊際環境損害要夠大，政 府才會課徵污染稅，否則政府就不會對廠商課徵污染稅，若邊際環境損害越大， 政府訂定的污染稅會越高。當市場存在多家民營廠商及一家公營廠商時，發現若 民營廠商家數增加會使得公營廠商減產，但對民營廠商的產量沒有影響，且民營 廠商的家數並不會影響到最適污染稅。此外，若市場存在一家民營廠商及一家部 分公營化的廠商，可以發現，污染稅若提高則民營廠商會減產，但公營廠商的產 量取決於民營化程度，而最適污染稅會隨著民營化程度提高而增加。;This dissertation analyzes the differences between a firm’s production and pollution control decisions in a mixed oligopoly market.And how the government imposes the pollution tax. This dissertation finds that in a mixed duopoly market, the higher the pollution tax imposed by the government, the lower the production of a private firm and the increase in public firm. The marginal environmental damage must be large enough for the government to impose a pollution tax, otherwise the government will not impose a pollution tax on firms. If the marginal environmental damage increases, the pollution tax imposed by the government will be higher. When there are many private firms and one public firm in the market, it is found that if the number of private firms increases, the output of public firm will be reduced, but it does no effect on the output of private firms. Moreover, the number of private firms does not affect the optimal pollution tax. In addition, if there is a private firm and a privatization firm in the market, it can be found that if the pollution tax is increased, the private firm will reduce output, but the output of the privatization firm depends on degree of privatization, and the optimal pollution tax will increase with the degree of privatization.
