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RE: st: Stata 11 Random Effects--Std. Errors


From   sofia <sofiagalligani@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   RE: st: Stata 11 Random Effects--Std. Errors
Date   Fri, 18 Feb 2011 08:48:53 -0800 (PST)

I find the post below very useful. 
I am still confuse with regards to xtreg, fe. I keep reading contradicting
statements. 
How to correct for autocorrelation? 
Thank you,
Sofia


David M. Drukker wrote:
> 
> This post continues the thread about robust standard errors for the
> generalized least-squares estimator implemented in -xtreg ,re-.
> 
> Eric de Souza <eric.desouza@coleurope.eu> asked whether there will be
> separate -vce()- options on -xtreg, re- to produce consistent estimators
> of
> the variance-covariance of the estimator (VCE) when the errors are
> heteroskedastic and when the errors are serially correlated.
> 
> The answer is yes, there will be separate options for these cases.
> 
> We will add a new -vce()- option for -xtreg ,re- that will produce the
> observation-level robust estimator that is consistent in the presence of
> some types of heteroskedasticity with -xtreg, re-.  This observation-level
> robust estimator was produced by -vce(robust)- in Stata 10.1.
> 
> In the Stata 11 -xtreg ,re-, we changed the meaning of the -vce(robust)-
> to
> be a synonym for -vce(cluster panelvar)-.  We made this change because
> researchers increasingly expect this definition of robust.  As Cameron and
> Trivedi (2005, section 21.2.3) and Wooldridge (2002, section 10.4.2) make
> clear, this individual-level robust estimator of the VCE is the natural
> "robust" estimator when sampling vectors of observations from individuals
> in
> the population.  This VCE estimator is robust at the individual-level
> instead of at the observation level.  This individual-level robust
> estimator
> of the VCE is more attractive in most real-world cases than the
> observation-level robust estimator because sampling is performed at the
> individual level.  This individual-level robust estimator is consistent in
> the presence of heteroskedasticity and autocorrelation.
> 
> Summing up, when specified with -xtreg re-, -vce(robust)- will continue to
> be a synonym for -vce(cluster panelvar)-.  We will add a new, as yet
> unnamed, -vce()- option that will produce the observation-level robust VCE
> estimator that is robust to some types of heteroskedasticity.
> 
> 
>    David
>    --ddruker@stata.com
> 
> 
> References
> ----------
> 
> Cameron, A. C.  and P. K. Trivedi. 2005. Microeconometrics: Methods and
> Applications.  New York: Cambridge University Press.
> 
> Wooldridge, J. W. 2002. Econometric Analysis of Cross Section and Panel
> Data.
> Cambridge, MA: MIT Press.
> 
> 
> 
> 
> 
> 
> 
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> 
> 

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