The standard errors that stata report are the standard Arellano-Bond 2-step estimator
standard errors.，there is evidence in the literature that the standard errors for the
two-step estimator may not be reliable.

[此贴子已经被作者于2009-1-14 14:38:52编辑过]

Please tell me something more about this  mater.

Your meaning is that that situation may be normal ,maybe need not solved, yes ?

thank you!