Dynamic Mechanism Design for a Global Commons

We model dynamic mechanisms for a global commons. Countries benefit from both consumption and aggregate conservation of an open access resource. A country's relative value of consumption-to-conservation is privately observed and evolves stochastically. An optimal quota maximizes world welfare subject to being implementable by Perfect Bayesian equilibria. With complete information, the optimal quota is first best; it allocates more of the resource each period to countries with high consumption value. Under incomplete information, the optimal quota is fully compressed --- initially identical countries always receive the same quota even as environmental costs and resource needs differ later on. We show that this is true even when private information is negligible.