在stata上运行xtabond2命令得到的结果
Sargan test of overid. restrictions: chi2(20)   = 358.25  Prob > chi2 =  0.000
  (Not robust, but not weakened by many instruments.)
Hansen test of overid. restrictions: chi2(20)   =  71.23  Prob > chi2 =  0.000
  (Robust, but can be weakened by many instruments.)
这样的检验结果说明了工具变量有效还是无效？新手不懂，谢谢！