st: Technical Efficiency with Stata sfpanel command

[Aristeidis dadoukis <a_dado12@yahoo.co.uk>]

Dear Statalist members,

I am new to Stata, so far I was using the Frontier 4.1 software.  I am interested in estimating an input oriented distance function using the Battese and Coelli (1995) model specifications, and then deriving scale efficiencies for individual banks.  

My model includes 3 inputs (x), 3 outputs(y) and 3 exogenous variables(z).  I have prepared the data for the translog function in the same way as when using the Frontier 4.1 software (ie arithmetically mean adjusting the inputs/outputs and generating the translog terms).  My sample covers  8 years and 15 obs per year.

However, when using the sfpanel command the MLE does not converge.  The command that I used is the following (please note that I also included the translog terms in the command)

sfpanel lnx1 lnx2 lnx3 lny1 lny2 lny3, model(bc95) emean(z1, z2, z3)

I would appreciate any advice on what might be wrong.

Aslo, what are the steps for estimating the scale efficiencies through Stata?  

Thanks and regards
Aristeidis Dadoukis


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