panel unit root tests make absolutely no sense with T=2. You are
looking for the long run behavior of a time series, and you have two
observations on the time series. No way to do that. After all, even a
Dickey-Fuller test on a single time series implies regressing the
difference in X on the lagged level of X, and you have precisely one
observation for that regression.
Kit
Kit Baum, Boston College Economics and DIW Berlin
http://ideas.repec.org/e/pba1.html
An Introduction to Modern Econometrics Using Stata:
http://www.stata-press.com/books/imeus.html
On May 3, 2008, at 02:33 , statalist-digest wrote:
>
> I tried the levin-lin test. Unfortunately, I get an error message :
>
> . sort id year
>
> . tsset id year
> panel variable: id (strongly balanced)
> time variable: year, 2004 to 2005
>
> . levinlin csp, lags(1)
>
> Levin-Lin-Chu test for csp Deterministics chosen: constant
> Reducing Andrews truncation
> no observations
> r(2000);
>
> . describe csp
>
> storage display value
> variable name type format label variable label
> -
> ----------------------------------------------------------------------
> ---------
> csp float %9.0g CSP
>
> Do you have any idea what the problem could be?
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