The efficiency of voluntary pollution abatement when countries can commit

We characterize a mechanism for reducing pollution emissions in which countries, acting non-cooperatively, commit to match each others' abatement levels and may subsequently engage in emissions quota trading. The mechanism leads to an efficient level of emissions, and if the matching abatements process includes a quota trading stage, the marginal benefits of emissions are also equalized across countries. Given equilibrium matching rates, the initial allocation of emission quotas (before trading) reflects each country's marginal valuation for lower pollution relative to its marginal benefit from emissions. These results hold for any number of countries, in an environment where countries have different abatement technologies and different benefits from emissions, and even if the emissions of countries are imperfect substitutes in each country's damage function. In a dynamic twoperiod setting, the mechanism achieves both intra-temporal and inter-temporal efficiency. We extend the model by assuming that countries are voluntarily contributing to an international public good, in addition to undertaking pollution abatements, and find that the level of emissions may be efficient even without any matching abatement commitments, and the marginal benefits of emissions may be equalized across countries even without quota trading