A National, Longitudinal Study of the Effects of Concentrated Hog Production on Ambient Air Pollution
利用1980-2002年美国生猪产业集中度的地理变化，研究发现每平方英里生猪数量翻倍会导致硫基空气污染增加6.6%，外部性成本超过监管要求，表明监管可带来社会收益。
Abstract The Environmental Protection Agency is considering regulation of large‐scale hog producers under the federal Clean Air Act, but little is understood about livestock's effects on ambient air quality at the national level. I use the geographic changes in swine industry concentration between 1980 and 2002 to identify ambient air pollution attributable to this industry, controlling for numerous other factors. Doubling the number of hogs per square mile yields a 6.6% increase in sulfur‐based ambient air pollution. Externality costs are estimated to be greater than possible regulatory requirements, suggesting societal gains from regulation.