The Triple Inefficiency of Uncoordinated Environmental Policies

When pollution is transboundary and there is international trade, a domestic inefficiency may arise in addition to the well‐known inefficiencies at the international level. More precisely, there will be a Nash equilibrium in which each country chooses a policy that gives it lower welfare than would otherwise be possible given the emission levels of all countries. However, there will also be a Nash equilibrium in which each country chooses tradable emission quotas as its policy instrument to achieve its desired level of emissions. In this Nash equilibrium, welfare in each country is maximised given the emission levels of all countries.