摘要：Environmental policymakers must address the adverse effects of a number ofpollutants that accumulate in the environment. Goals for the regulation of these damagesoften involve holding long-term emissions below a level deemed to be "dangerous,'' oroutright banning of offending products or processes along with subsidization of more "green"alternatives. This paper builds upon previous studies by Keeler, Spence, and Zeckhauser(1971) and Tahvonen and Withagen (1996) in addressing the optimal long-term managementof an accumulative but assimilatable pollutant through policies that restrict more damagingproduction processes and thereby induce more benign alternatives. Using a simple generalequilibrium approach, we consider the possibility that the assimilative capacity of theenvironment is diminished and eventually exhausted by pollution accumulation. In this casethere is a nonconvexity in the problem that gives rise to multiple potential optima,complicating the characterization of the optimal path and the determination of decentralizedpolicies that can support an optimal outcome. In particular, environmental quality may bepreserved or completely degraded in the long term. This makes the question of whetherpolluting processes or products should be banned more complicated and more interesting.We characterize the circumstances under which a banning policy is consistent with anintertemporally optimizing path, we investigate the sensitivity of optimal solutions to the costof a clean backstop technology, and we discuss more generally the design of price-based andquantity-based policies for supporting an optimal solution.
关键词：stock externalities; nonconvexities; sustainable development
