黃河泉 发表于 2018-12-27 10:45 
1. 请看看 xtabond2 中之 collapse 选项。2. AR(2) 没通过,不太好处理!
老师,您好。最近投了一篇论文,外审专家返回了一个修改意见,看不懂,请老师帮忙。
System GMM requires the additional assumption that the differences used as instruments are uncorrelated with the error term (in particular with the unobserved unit-specific effects). A sufficient condition for this to hold would be joint mean stationarity of the dependent variable and the independent variables, which may not be easily justifiable in this study.
翻译过来是这样:系统GMM需要额外的假设,即作为工具使用的差异与误差项不相关(特别是与未观测到的特定单位效应无关)。一个充分条件是因变量和自变量的联合平均平稳性,这在本研究中可能不容易证明。
请问这个问题怎么解决呢?烦求老师解惑,谢谢