存在環境污染下的公營廠商最適民營化政策

THE OPTIMAL PRIVATIZATION POLICY IN THE PRESENCE OF ENVIRONMENTAL DAMAGE

本文探討廠商生產過程會對環境產生污染的情形下，政府的最適民營化政策。假設市場上存在一家公營廠商及一家民營廠商，廠商生產過程會排放污染對環境有所損害，兩廠商在市場上進行Cournot數量競爭，政府基於社會福利考量下決定一最適的民營化政策。本文發現，存在環境汙染下，民營化不一定會使公營廠商減產且產量不一定會比民營廠商的產量多。當生產的邊際環境損害夠大時，本文得到與傳統民營化文獻不同的結果，即民營化程度提高會使公營廠商增產，民營廠商減產。其次，民營化不一定能改善環境。當生產的邊際環境損害夠大（小），則民營化後會使環境惡化（改善）。此外，只要環境損害函數為線性函數，則最適民營化程度完全不受污染的邊際損害程度大小而有所影響；然而，若環境損害函數為遞增（遞減）函數，最適民營化程度會隨著單位污染程度增加而提高（降低）。

This paper analyzes the optimal privatization policy for a public firm given that environmental pollution will emerge during the production process. We consider a mixed oligopoly where a public firm and a private firm engage in Cournot competition. We find that if pollution accompanies the production process, in contrast to the conventional wisdom, privatization may not decrease the output of the privatized public firm. Furthermore, whether privatization will improve environmental quality is ambiguous. It will make the environment worse off (better off) if the marginal environmental damage of production is large (small). In addition, the optimal degree of privatization is independent of the marginal damage of pollutant if the environmental damage function is linear. The optimal degree of privatization will be larger (smaller) than that without pollution if the environmental damage function is convex (concave).