Politique environnementale en économie ouverte. Une possible incompatibilité entre les décisions des firmes et des gouvernements

We examine the design of national emission taxes in an international trade setting with imperfect competition and trade costs. The main point of the paper is that there can exist a consistency problem with respect to tax policy in a setting where trade costs are positive. In particular, when firms make production decisions in response to tax policy, there exists a range of trade costs such that the optimal tax for a given trading outcome (autarky or trade) does not induce that trading outcome in equilibrium. This range is wider as the markets are less competitive. We also show that environmental taxes are higher when markets are open, nevertheless, at positive trade costs, social welfare is lower than in autarky. Classification JEL : C62 ; F12, F18, H21