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Re: st: two stage model variance estimators


From   "Rachel Bouvier" <rbouvier@usm.maine.edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: two stage model variance estimators
Date   Sat, 17 Sep 2005 09:13:31 -0400

Thank you so  much!  I will try that.  -Rachel

Rachel Bouvier
Assistant Professor of Economics
University of Southern Maine
11 Chamberlain Avenue
Portland, ME 04104
(207) 228-8377
>>> mshanson@mac.com 09/17/05 8:11 AM >>>
On Sep 16, 2005, at 8:04 AM, Rachel Bouvier wrote:

> The original project was to try and get a "trend" of GDP over
> time, with the residuals as the fluctuations around that trend.  Then,

> I
> would use both the trend and the flucuations as regressors in my
second
> stage model.  Again, this was a few years ago, and I am trying to dust
> off the model and see if it makes sense to revisit it.  I know a lot
> more now than I did then - I'm going to have to rethink the whole 
> thing.
>  I wish I had consulted Statalist then!

	If you have enough data in the time dimension to estimate
separate 
trends per country, you may want to consider taking natural logs of 
your GDP data and then linearly detrending (i.e. regressing against 
time instead of both time and time^2).  Odds are GDP exhibits compound 
growth, so using a quadratic is just an approximation anyway -- and not 
necessarily a good one -- to an underlying exponential growth function. 
  Additionally, when you use logs your estimated coefficients will have 
elasticity interpretations, which are useful (as they are unit-free) in 
cross-country studies.  Hope this helps.

                                         -- Mike

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