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Re: st: RE: RE: estimation with a time trend.


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: RE: estimation with a time trend.
Date   Mon, 5 Jul 2010 14:52:51 +0000 (GMT)

--- On Mon, 5/7/10, natasha agarwal wrote:
> I was wondering then what is the point in doing this then?


This thread is getting very confused. Let me try
to reconstruct the argument:

You asked about estimating a time trend by first
creating a variable using -egen group()-. Now
we had to guess why you would want to do that. 
We guessed that you wanted to make sure that your
time has the value 0 at some a meaningful point
in time. Which in general is good, though it 
doesn't matter if you used a fixed effects model
without interactions (it does matter if you 
include interactions with time).

Even though making sure that time has a meaningful
0 value is a good idea, using -egen group()- for
that is a very dangerous idea, and you should never
do that. Instead you should just substract some
meaningful 'midpoint' or 'reference year'.

So, to clear up this thread:
Why did you want to use -egen group()-?

-- Maarten

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

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


      

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