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....

In the half century since the founding of the U.S. Environmental Protection Agency, public and private U.S. sources have spent nearly $5 trillion ($2017) to provide clean rivers, lakes, and drinking water, or annual spending of 0.8 percent of U.S. GDP in most years. Yet over half of rivers and...