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st: why predictnl calculates different values?

From   Sasha Shepotylo <>
Subject   st: why predictnl calculates different values?
Date   Mon, 27 Jul 2009 10:08:42 +0300

Dear Statalist users,

I have a panel 2000-2008 of some bilateral exports
l estimate the model by hausman-taylor:

 xhhtaylor ...

Then I predict

predictnl yhat1=exp(predict(xbu))

Then I change the value of some explanatory variable x but only for
years after 2003:

replace x=c if year>=2004

and predict again

predictnl yhat2=exp(predict(xbu)).

To my surprise, yhat2 is different from yhat1 for 2000-2003 periods.
How should I interpret these results?
My guess is that when I change some value of x in the future, it
changes the whole variance-covariance matrix and this is what drives
the results.
If it is true, does it have any economic interpretation?



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