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Arellano-Bond test for AR(1) in first differences: z = -14.74 Pr > z = 0.000
Arellano-Bond test for AR(2) in first differences: z = 1.11 Pr > z = 0.268
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Sargan test of overid. restrictions: chi2(94) = 410.03 Prob > chi2 = 0.000
(Not robust, but not weakened by many instruments.)
Hansen test of overid. restrictions: chi2(94) = 213.87 Prob > chi2 = 0.000
(Robust, but weakened by many instruments.)
系统GMM的Hansen检验老是为0,应该是工具变量的选择出现了问题,但是初学计量,对工具变量的选择不得要领,简单得将控制变量滞后2~ 5期作为工具变量。截面数近3000,工具变量共115个。
此外解释变量是M2,因为研究对象是上市公司,因此我视为了严格外生变量。
向各位老师和前辈请教,应该如何去调整?


雷达卡





,一般减少工具变量的数量即可,可以减少内生变量数,也可以减少滞后期数。
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