Optimal Policy with Tradable and Bankable Pollution Permits: Taking the Market Microstructure into Account

This paper analyzes how the way emission permits are traded—their market microstructure—affects the optimal policy to be adopted by the environmental agency. The microstructure used is one of a quote driven market type, which characterizes many financial markets. Market makers act as intermediaries for trading the permits by setting an ask price and a bid price. The possibility of bank permits is also introduced in our dynamic two‐period model. We consider two models whether the market makers are perfectly informed about the technology of the producers or not. When the market makers have complete information, the equilibrium price of permits is the same as if the market is walrasian. When they are imperfectly informed, they may set a positive spread between bid and ask permit prices, which creates some inefficiency as the marginal abatement costs of polluters do not equalize. By allowing more flexibility in the use of the permits, banking may reduce the spread. Moreover, it may introduce price rigidities due to intertemporal arbitrage. In this framework, the circumstances under which banking should be allowed or not depend crucially on the evolution of the marginal willingness to pay for the environment.