污染稅與污染標準的福利比較：上游廠商市場結構與政策協調的角色

Welfare Comparison of Emission Taxes and Emission Standards: Role of Upstream Firms' Market Structure and Policy Coordination

本文修改自Fujiwara (2010)的兩國跨界污染相互傾銷模型，納入上游廠商的訂價決策與污染排放許可量的設定，重新比較污染稅與污染排放許可量的福利大小。首先，當兩國非合作制訂最適環境工具時，若上游廠商為完全競爭市場，污染稅的福利低於污染排放許可量；若為獨占市場，當跨界污染程度與邊際污染損害的交互影響程度較小(大)時，污染稅的福利高(低)於污染排放許可量。其次，當兩國合作制訂最適環境工具時，若上游廠商為完全競爭市場，兩種政策的福利相同；若為獨占市場，污染稅的福利大於污染排放許可量。由此可知，無論兩國是否合作制訂環境工具，上游廠商的市場結構始終扮演重要角色。此外，當上游市場為完全競爭或獨占時，兩國是否合作也會影響污染稅與污染排放許可量的福利比較。

This study modifies Fujiwara’s (2010) reciprocal dumping model of transboundary pollution by incorporating upstream firms’pricing decisions and emission standards and conducted a welfare comparison between emission taxes and standards. First, in a noncooperative framework, when the upstream market is perfectly competitive, the level of welfare is lower under an emission tax policy than under an emission standards policy. However, in a monopolistic market, the level of welfare is higher (lower) under an emission tax policy than under an emission standards policy when the interaction between transboundary pollution and marginal pollution damage is smaller (larger). Second, under a cooperative framework, the level of welfare is identical under both policies in a perfectly competitive market but higher under the emission tax policy in a monopolistic market. These results highlight the crucial role of the upstream market structure, which influences welfare levels regardless of the level of cooperation between countries. Additionally, cooperation affects the welfare comparison between taxes and standards in both market structures.