Re: st: Re: Time invariant variables and panel data

["Christer Thrane" <ch-thran@online.no>]

First q: yes
Second q: No, I don't think so. FE utilizes the changes within persons, so 
if thing don't change, FE is not viable.

CT
----- Original Message ----- 
From: "Rho YH" <mania1@korea.ac.kr>
To: <statalist@hsphsun2.harvard.edu>
Sent: Saturday, May 27, 2006 7:44 PM
Subject: RE: st: Re: Time invariant variables and panel data



> To be sure, are the "random effects" and "fixed effects" of the answer 
> the -RE and -FE options of xt-
> series commands?
> Also, as xtgee does not have such option, then can I use time invariant 
> variables anyway?
>
> > ---- Original Message ----
> > From : Christer Thrane [ch-thran@online.no]
> > To : statalist@hsphsun2.harvard.edu
> > Date : 2006�� 5�� 28��(��) 01:38:38
> > Subject : st: Re: Time invariant variables and panel data
> >
> >
> > Hi,
> >
> > If you estimate random effects models, you can have both time-varying and
> > time-invariant variables on the right hand side.
> >
> > If you estimate fixed effects models, you must have time-varying on the
> > right hand side. But fixed effects also handles interactions between
> > time-varying and time-invariant right hand side variables. (Then the
> > interaction is no longer time-invariant.)
> >
> > Take a look at Woldridge's Basic Econometrics. A modern introduction--it's
> > on Stata website.
> >
> > HTH
> >
> > Christer
> > ************************************************
> > Professor Christer Thrane
> > Department of Social Science
> > Lillehammer University College
> > 2626 Lillehammer, Norway
> > + 47 61 28 81 70 (fax)
> > + 47 61 28 82 47 (phone, work)
> > + 47 61 25 53 04 (phone, home)
> > E-mail, work: christer.thrane@hil.no
> > E-mail, home: ch-thran@online.no
> > ************************************************
> >
> >
> >
> > ----- Original Message -----
> > From: "Rho YH"
> > To:
> > Sent: Saturday, May 27, 2006 4:48 PM
> > Subject: st: Time invariant variables and panel data
> >
> >
> > > I have incidentally found that panel data models (as far as I found the
> > > Statalist, xtreg with -FE option)
> > > cannot have time invariant variables and will be automatically omitted
> > > when included.
> > > In a general sense, then all xt- models (including xtgee) cannot have 
> > > time
> > > invariant variables?
> > > Or in what instance does this fact come in effect?
> > > Second, then does this mean that I cannot use time invariant variables
> > > (like sex (M/F)) even
> > > when these variables may be important?
> > > I have two books about panel data (Twisk, and Sophia Rabe-Hesketh) but 
> > > did
> > > not find this fact.
> > > Is it written in these books?
> >
> > *
> > * For searches and help try:
> > * http://www.stata.com/support/faqs/res/findit.html
> > * http://www.stata.com/support/statalist/faq
> > * http://www.ats.ucla.edu/stat/stata/

*
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