st: predicting efficiency with xtfrontier

["joserra coco" <pereastroika@hotmail.com>]

Hi everybody,

I was wondering if anybody could offer some guidance on two problems I have 
dealing with xtfrontier.

Using panel data, I am trying to estimate technical efficiency for a group 
of firms, over 10 years. The main problem I encounter is that, when I 
predict the technical efficiency scores, I get a single value for each firm, 
instead of one value per firm per year. My understanding is that if I use 
the time varying efficiency option (tvd), these values should be different 
within firms from year to year. This is an example of the code I use.

xtfrontier lny lnk lnl lnm , tvd iterate(26)
predict efficiency, u

Alternatively, I have also tried to include time dummies to account for 
technical progress. Same situation.

I would appreciate any guidance on this matter. Also, once I reach the 
technical scores, I would like to make them dependent on a set of firm 
attributes (not the ones I have used in the stochastic production frontier). 
Is this supposed to be a separate analysis that cannot be estimated through 
xtfrontier?.

Thanks a lot for any feedback.
Joserra.

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