Evaluating US Regulations: A Comment on Joseph S. Shapiro’s “Pollution Trends and US Environmental Policy: Lessons from the Past Half Century”

This article is a comment on Shapiro’s “Pollution Trends and US Environmental Policy: Lessons from the Past Half Century.” It first provides some historical perspective by comparing Shapiro’s analysis and conclusions to an article published 20 years ago by A. Myrick Freeman III. It then discusses (and slightly reframes) Shapiro’s four hypotheses and highlights the importance of understanding the counterfactuals implied by each hypothesis. Finally, it suggests at least one key lesson that emerges from Shapiro’s analysis and its implications for future work—namely, the need not only to improve methods and data for analyzing existing regulations but also to increase efforts to reduce currently unregulated sources of pollution, such as agricultural pollution and greenhouse gas emissions.