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Re: st: RE: RE: estimation with a time trend.
From
natasha agarwal <[email protected]>
To
[email protected]
Subject
Re: st: RE: RE: estimation with a time trend.
Date
Mon, 5 Jul 2010 16:19:15 +0100
I am really really sorry for this confusion what I have created here.
I wanted to introduce a time trend in my estimation where my years go
from 2001-2005. I was estimating an augmented production function
using an unbalanced panel data using a within estimator.
With time trend I mean:
panel identifier year time trend
1 2001 1
1 2002 2
1 2003 3
1 2004 4
1 2005 5
2 2001 1
2 2002 2
The only way I knew how to do it was to use the egen -group-
command.That is why I wanted to do the egen-group- command.
However I was not confident whether the creation of the same was
correct because of the unbalanced nature of the data.
for the purpose of estimating my equation I issue the following command:
egen t=group(year)
xtreg lnrval lnk lnw lnvfdi t, fe vce(robust)
Thanks
Natasha
On Mon, Jul 5, 2010 at 3:52 PM, Maarten buis <[email protected]> wrote:
> --- 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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