另:数据库合并 可参考:https://bbs.pinggu.org/thread-5873178-1-1.html。
文中的步骤是对,BRANDT(Brandt, L., et al. (2012). "Creative accounting or creative destruction? Firm-level productivity growth in Chinese manufacturing."Journal of Development Economic 97(2): 339-351.)的重要解释补充。