Why Is Pollution from US Manufacturing Declining? The Roles of Environmental Regulation, Productivity, and Trade
研究发现1990至2008年间美国制造业空气污染排放下降60%，主要源于产品内排放强度降低，而非产出或产品结构变化；环境规制（隐含污染税翻倍）是主因，生产率和贸易影响较小。
Between 1990 and 2008, air pollution emissions from US manufacturing fell by 60 percent despite a substantial increase in manufacturing output. We show that these emissions reductions are primarily driven by within-product changes in emissions intensity rather than changes in output or in the composition of products produced. We then develop and estimate a quantitative model linking trade with the environment to better understand the economic forces driving these changes. Our estimates suggest that the implicit pollution tax that manufacturers face doubled between 1990 and 2008. These changes in environmental regulation, rather than changes in productivity and trade, account for most of the emissions reductions.