On Wed, 2 Dec 2009, Zhang Yan wrote:
Dear
I am Zhangyan, a PhD candidate in Economics.
I am using levpet to calculate TFP. But stata said
"
. tsset frdm year
panel variable: frdm (unbalanced)
time variable: year, 2005 to 2007, but with gaps
delta: 1 unit
. levpet lnva, free( lncyry lnage) proxy( lnzjtrj) capital(lngdzch) valueadded i
(frdm) t(year) reps(250)
repeated time values within panel
r(451);
"
If Zhangyan would send the dataset directly to me ([email protected]), I'd be
happy to look into the cause of this error message.
However, note that here the dataset has only three time periods, with
gaps. I strongly suspect that with very short panels together with gaps
in the data, -levpet-, -opreg-, and similar productivity estimators will
produce very imprecise estimates.
-- Brian Poi
-- [email protected]
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