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


From   natasha agarwal <agarwana2@googlemail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: RE: estimation with a time trend.
Date   Mon, 5 Jul 2010 13:45:16 +0100

On Mon, Jul 5, 2010 at 1:14 PM, Maarten buis <maartenbuis@yahoo.co.uk> wrote:
> --- On Mon, 5/7/10, natasha agarwal wrote:
>> I am afraid I did not understand "year- (or -year-
>> MINUS> midpoint) for interpretability?"
>
> Say you have a variable representing year of birth
> ranging between 1910 and 1980. I would then usually
> have a line like this in my do-file:
>
> gen c_year = year - 1910
>
> Afterwards I would use c_year instead of year. In
> this case "midpoint" is 1910, and makes sure that
> your new variable is shifted to the left such that
> it has the value zero in 1910. This makes sure
> that the baseline in your models refer to a point
> at the beginning of your observed period. This is
> particularly important if you include interactions
> or if you care about the constant (e.g. in a random
> effects model)

I am estimating the model with a within estimator. I thought that they
mean center the data anyways?



> 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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