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Re: st: Binary Variables


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Binary Variables
Date   Wed, 2 Jun 2010 04:16:13 -0700 (PDT)

--- On Wed, 2/6/10, Natalie Trapp wrote:
> I use a Dummy Variable for 150 regions within the EU27.
> When I regress the model, I use one region as a reference
> group, but Stata still automatically omits four to five more
> regions. Is it maybe because the regions are too similar in
> their characteristics so that I have to build groups of
> similar regions? Or is there another way how I can do the
> regression with all regions of interest?

This is a fixed effects regression (assuming you are using 
linear regression, -regress-).  This type of regression can 
only make use of variation within a region, so if the dependent
variable is constant within a region, the region will be dropped.
Your alternative is to use random effects regression (see:
-help xtreg-), but that has disadvantages of its own. It is up 
to you to decide which disadvantages you think are least bad... 

Hope this helps,
Maarten

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://www.maartenbuis.nl
--------------------------


      

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