環境品質標準與貿易自由化

Environmental Quality Standard and Trade Liberalization

本文建立一個兩國兩廠商進口模型，以探討貿易自由化下政府的最適環保產品的認證政策及相關福利效果。在模型中，有一家外國廠商將其生產之產品出口到本國市場，與本國廠商從事Cournot競爭，且本國政府對進口產品課徵關稅。我們分別討論了兩種情境：1.本國政府採取單一環境品質標準，與2.本國政府允許差別環境品質標準。我們發現，本國調降關稅會使環境品質標準提高，對廠商利潤的影響為不一定，當產量效果大於（小於）品質效果，則廠商利潤會下降（上升），此外，調降關稅對總汙染的影響，以及對本國社會福利的影響均為不一定。本文進一步對兩情境下的各項均衡值進行比較。結果發現，若本國允許外國產品不需通過本國的標準亦可進口，則外國不會訂環境品質標準，當消費者對污染的知覺的程度較小（大）時，單一環境品質標下的環境品質標準會較差別品質標準嚴格（寬鬆），此外，本國的社會福利在單一品質標準高於差別品質標準時。

This paper develops a two-country two-firm importing model to discuss the optimal certification environmental standard and the associate welfare effects of trade liberalization. In the model, a foreign firm exports goods with consumption externality to domestic market and engages in Cournot competition with domestic firm. We discuss two scenarios: 1. domestic government sets uniform quality standard to be followed by the two firms, 2. Domestic allows foreign firm with different quality standard from that of domestic to import. We find, the foreign government will not set the quality standard when the domestic government allow differentiate standards, and the ranking of the two standards of the two scenarios depends on the awareness of the domestic consumers on the pollution of the goods, when the awareness of the domestic consumers is low(high), the quality standard under uniform standard policy is higher (lower) that under differentiate standard policy. The effect of tariff reduction on the firms' profit depends on the output effect and environmental quality cost effect, when the output effect dominates (is dominated by) the environmental quality cost, the profit of the firms will go down (up). The effect of tariff reduction on total pollution and domestic social welfare are ambiguous. Further, quality standard in first situation is stricter. However, if the level of consumer awareness is high, the environmental quality standards in second situation is more stringent. Finally, domestic social welfare always higher in the first situation.