Over the past decade, concern over potential global warming has focused attention on the emission of greenhouse gases into the atmosphere, and there is an active debate concerning the desirability of reducing emissions. At the heart of this debate is the future path of both greenhouse gas...

A policy considered in isolation may be ineffective because of the countervailing impact of other factors. And the success of a policy may itself lead to perverse incentives. Thus it is important to design complementary policies that support the original goal. Controlling air pollution from...