跨國污染與貿易同盟

Cross-Border Externalities and Trade Union

本文建構一個三國兩廠的寡占市場模型，模型包含只消費的本國，和從事生產的低污染北國與高污染南國，且此產品的生產過程會產生跨國境的污染。文中分別分析在本國可自由課徵兩國關稅、最惠國待遇原則下課徵統一關稅、與北國簽定區域貿易協定、與南國簽定區域貿易協定等四種情形下，最適關稅率與福利的分析與比較。文章並進一步研究在北國提高環保標準、污染防治技術進步與污染外溢效果加重等三種狀況下，對南北兩國與對本國的影響。研究主要結果為：第一，若北國廠商的污染防治比例對北國污染稅率的敏感度愈高，而北國政府提高環保標準，則北國利潤上升的可能性愈大。對南國而言，單一關稅下利潤增加，其他情形下，利潤惡化的可能性提高。第二，若本國將環境品質納入福利函數中，採行不同的貿易措施下之福利效果，最好的為對南、北兩國自由課稅，次佳為最惠國待遇下採用單一關稅，再其次為與北國自由貿易，最差者為與南國自由貿易。

This paper constructs a 3-country, 2-firm oligopoly model whichconsists of a home country with no production, a low-polluted northcountry, and a high-polluted south country. Trans-boundary pollutions tothe home country are presumed. Optimal tariff and social welfare areanalyzed under the following four cases: 1. the home country imposedifferential tariff, 2. union tariff to obey the most favored nation principle,3. trade union with the north country, 4. trade union with the southcountry. In addition, the effects of increasing pollution tax by the northcountry, improved technology of pollution-abatement, and cross-borderpollution increase on the profit and social welfare are studied. The resultsindicate that if the north firm’s abatement ratio is more sensitive to thepollution tax, then the north country will likely improve welfare by northgovernment’s raise of pollution tax. As for the south country, the profit willbe improved under uniform tariff situation and decreased under the othercases. For the home country, if environmental quality is considered in thewelfare function, the welfare will be increased most by imposingdifferential tariffs, secondly by adopting uniform tariff, thirdly by free tradewith the North, and least by free trade with the South.