In the 1960s, there were worries that U.S. economic growth would lead to increasingly dangerous levels of pollution, and that by the year 2000, air pollution would make cities like Los Angeles and New York uninhabitable. Instead, U.S. air quality has improved dramatically since then. The U.S. Environmental Protection Agency estimates that the reduction in U.S. air pollution since 1990 prevented several hundred thousand premature deaths annually, so it is important to understand its causes. How do U.S. manufacturers produce more now, while polluting less?
