问题描述：
英语翻译
In particular,this occurs when the lagged levels of the series are weakly correlated with subsequent first-differences as normally happens when the series is highly persistent.
The first-differenced GMM estimator has been found to have poor fi nite
sample properties in terms of bias and imprecision.In particular,this occurs
when the lagged levels of the series are weakly correlated with subsequent fi rstdifferences as normally happens when the series is highly persistent.Hence the
instruments available for the fi rst-differenced equations are weak (Blundell and
Bond,1998).Blundell and Bond have shown that the fi rst-differenced GMM
estimator could be subject to a large downward bias.This is particularly severe
when the time period being considered for each unit is small.For example,in most
cross-country growth regressions,the time period is reduced to a small number of
τ-period averages as in our case.这是这句话的上下文，输入不了太多了。
In particular,this occurs when the lagged levels of the series are weakly correlated with subsequent first-differences as normally happens when the series is highly persistent.
The first-differenced GMM estimator has been found to have poor fi nite
sample properties in terms of bias and imprecision.In particular,this occurs
when the lagged levels of the series are weakly correlated with subsequent fi rstdifferences as normally happens when the series is highly persistent.Hence the
instruments available for the fi rst-differenced equations are weak (Blundell and
Bond,1998).Blundell and Bond have shown that the fi rst-differenced GMM
estimator could be subject to a large downward bias.This is particularly severe
when the time period being considered for each unit is small.For example,in most
cross-country growth regressions,the time period is reduced to a small number of
τ-period averages as in our case.这是这句话的上下文，输入不了太多了。
问题解答：
我来补答展开全文阅读