環境污染型式、市場集中度與環境政策

POLLUTION PATTERN, MARKET CONCENTRATION, AND ENVIRONMENTAL POLICY

本研究利用一個Cournot數量競爭之寡占模型，探討環境污染型式與市場集中度對一國環境政策之影響。本文發現當污染損害函數為二次式時，其結果與污染損害函數為一次式時截然不同。污染損害函數為一次式的情形下，環境政策並不會因廠商為聚集型廠商或是分散型廠商而有所不同。然而，污染損害函數為二次式的情形下，當市場需求為線性時，聚集型廠商所面對的最適污染稅率會大於分散型廠商所面對的。此外，當需求曲線凸向（凹向）原點時，若廠商為「聚集型廠商」，則產業集中程度愈高，最適污染稅率愈小（大），若廠商為「分散型廠商」且污染損害係數相對較大，則市場集中度愈高，最適污染稅率愈大（小）。本文結果顯示污染損害的函數型式與市場集中度對最適環境政策具有關鍵性影響。

This paper analyzes how market concentration and pollution pattern affect the environmental policy in an asymmetric oligopoly. When the environmental damage function is linear, whether polluting firms are aggregate or dispersed does not affect the optimal environment policy. However, when the environmental damage function is quadratic, aggregated firms should face a higher pollution tax than dispersed firms as long as the market demand function is not too convex. Moreover, the pollution tax for aggregated firms de-creases (increases) with a higher market concentration when the demand function is convex (concave). However, the pollution tax for dispersed firms increases (decreases) with a higher market concentration and a relatively large damage parameter when the demand function is convex (concave). Therefore, the pollution pattern and market concentration crucially affect the optimal environmental policy.