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I wonder why areg and xtreg do not give the same standard errors with the robust option with version 10 and higher.
It seems that areg uses a different degrees of freedom adjustment.
Some people think on a stata forum that it could be due to an error with the "areg" estimation in newer versions.
On the other hand, stata help for areg command says that :
"areg is designed for datasets with many groups, but not a number of groups that increases with the sample size. See thextreg, fe command in [XT] xtreg for an estimator that handles the case in which the number of groups increases with the sample size."
Does anyone understand this?