Is Trade Good or Bad for the Environment? Sorting Out the Causality
利用地理因素作为工具变量，在控制GDP水平后，发现贸易倾向于降低二氧化硫和二氧化氮浓度，但对颗粒物影响不显著，总体没有证据表明贸易损害环境。
We seek to contribute to the debate over globalization and the environment by asking: What is the effect of trade on a country's environment, for a given level of GDP? We take specific account of the endogeneity of trade, using exogenous geographic determinants of trade as instrumental variables. We find that trade tends to reduce three measures of air pollution. Statistical significance is high for concentrations of SO 2 , moderate for NO 2 , and lacking for particulate matter. Although results for other environmental measures are not as encouraging, there is little evidence that trade has a detrimental effect on the environment. © 2005 President and Fellows of Harvard College and the Massachusetts Institute of Technology.