刚好看到一篇文章Xinzheng Shi, Zhufeng Xu, 2018,Environmental regulation and firm exports: Evidence from the eleventh Five-Year Plan in China, Journal of Environmental Economics and Management. Volume 89, Pages 187-200.作者找了一个通风系数(ventilation coefficient)作为环境规制力度(policy intensity)工具变量,这个变量是根据各省会城市的海拔高度和风速来估计污染扩散的程度,容易扩散的省,环境规制力度越小。
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