考慮外溢效果下以污染稅融通之環境政策

Environmental policies with financing emission tax under spillover effect

本文假設當政府以課徵污染稅來融通對廠商防治污染投入之補貼財源，並考慮廠商的防治污染技術存在外溢效果時，對一國政府制定環境政策將會有何影響。並藉此分析比較不同環境政策的產出效果、污染排放效果。根據本文所得之結果顯示，(1)在成本函數為可分割時：補貼對廠商最適產量不具任何影響，且補貼愈高，污染排放量就愈高。(2)倘若成本函數為不可分割時：政府所訂定的補貼率愈高，廠商的最適產量則會降低，然此項效果會因為外溢效果存在而抵消。另外，政府亦可透過補貼達到減少污染排放量之目的，不過，此項政策效果亦會受到外溢效果大小影響。

Spillover effect should be considered important to environmental policies. This paper investigates the optimal environmental policies when considering both subsidies on pollution abatement technology and spillover effects of the technology itself. In the analysis of backward induction on a two-stage game，two main results are obtained according to our findings. First，the government subsidy has no impact on the optimal production under the assumption of separable cost function. Second，the optimal production is lower when the government subsidy is higher under an inseparable cost function.