許多策略性環境政策的相關文獻，大多在探討生產外部性的問題，較少著墨在消費的外部性，且在模型設定上，大多假設廠商生產同質性商品，因此本文將商品之差異性納入考量，在單邊貿易模型之下，建立一個兩階段賽局，來探討消費外部性的情況下，廠商與政府的策略性行為。而本文亦將貿易政策與環境政策做連結，探討當關稅因貿易自由化而調降時，對環境政策與環境品質的影響為何。
本研究發現：(1) 不論廠商的競爭型態為何，政府會將最適污染稅稅率訂在低於污染所造成的邊際環境損害之水準。(2) 不論廠商的競爭型態為何，貿易自由化會提升最適污染稅稅率。(3) 在廠商進行 Cournot 競爭時，貿易自由化將提升環境品質。(4) 在廠商進行 Bertrand 競爭時，關稅調降與否，須考量商品間的替代程度，在商品替代程度很低時，貿易自由化的結果將使環境品質向下沉淪。

This thesis develops a two-stage game to investigate the strategies of government and firms concerning negative externalities associated with consumption. It also discusses the linkages between trade liberalization and environmental policy, namely, the effect of tariff reduction due to trade liberalization on environmental policy and environmental quality. Most of the literature on strategic environmental policy only considers negative externalities associated with production, but this thesis deals with negative externalities associated with consumption.
Several conclusions emerge: First, the optimal pollution tax is less than the marginal pollution damage. Second, the environmental tax increases as a consequence of a tariff reduction. Third, if firms compete in terms of quantity, environmental quality could be improved by liberalizing trade. Finally, if firms compete in terms of price, when the degree of goods substitutability is low, trade liberalization may lead to a “race to the bottom” in environmental quality.

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