求助各位大神

用动态gmm xtabond2命令的AR(1) AR(2)不显示 只出现了一个. 请问是什么原因啊？

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Arellano-Bond test for AR(1) in first differences: z =      .  Pr > z =      .
Arellano-Bond test for AR(2) in first differences: z =      .  Pr > z =      .
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Sargan test of overid. restrictions: chi2(21)   =  44.10  Prob > chi2 =  0.002
  (Not robust, but not weakened by many instruments.)
Hansen test of overid. restrictions: chi2(21)   =  23.34  Prob > chi2 =  0.326


最后这里是这样显示的 请问应该怎么调整