Pollution Trends and US Environmental Policy: Lessons from the Last Half Century

This article proposes and evaluates four hypotheses about US pollution and environmental policy over the last half century. First, air and water pollution have declined substantially, although greenhouse gas emissions have not. Second, environmental policy explains a large share of these trends. Third, much of the regulation of air and drinking water pollution has benefits that exceed costs, although the evidence for surface water pollution regulation is less clear. Fourth, while the distribution of pollution across social groups is unequal, market-based environmental policies and command-and-control policies do not appear to produce systematically different distributions of environmental outcomes. I also discuss recent innovations in methods and data that can be used to evaluate pollution trends and policies, including the increased use of environmental administrative data, statistical cost-benefit comparisons, analysis of previously understudied policies, more sophisticated analyses of pollution transport, micro-macro frameworks, and a focus on the distribution of environmental outcomes.