International environmental agreements under an evolutionary mechanism of imitation and asymmetric countries

Under an often employed imitation mechanism, we investigate whether n countries with different emission abatement benefits and costs can achieve an international environmental agreement. When the abatement efficiencies, ancillary benefits of abatement, and/or the numbers of countries are large, an international environmental agreement with full participation is the unique long‐run equilibrium. For the remaining situations, either no agreement is the unique equilibrium or both equilibria above can emerge with positive probability. These results hold whatever the function forms of countries' abatement costs are, whether the transboundary pollution of emissions is considered, and whether the mutation rates depend on abatement costs and time.