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st: frontier model estimation (Battese & Coelli 92) + error message "initial values are not feasible"


From   "Kerstin Oriold" <kerstin.oriold@exes.co.at>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: frontier model estimation (Battese & Coelli 92) + error message "initial values are not feasible"
Date   Sat, 10 Apr 2010 16:29:47 +0200

Dear statalisters,

I have a problem in context with the frontier model estimation based on
Battese & Colli (1992) when working with a panel data set of 11 observations
over 12 years. Using the respective command: 

xtfrontier logpoints logbed logstaff logdischarges d98 d99 d00 d01 d02 d03
d04 d05 d06 d07 d08, tvd  i(dmu) t(year)

leads to the error message ?initial values are not feasible?. Can anybody
tell me how to handle this problem ?

If I choose a simpler estimation let?s say without the time dummies or
without logbeds:
xtfrontier logpoints logbed logstaff logdis, tvd  i(dmu) t(year)
xtfrontier logpoints logstaff logdischarges d98 d99 d00 d01 d02 d03 d04 d05
d06 d07 d08, tvd  i(dmu) t(year)

It does work, however, I would highly appreciate to find a solution for the
?original model? as the time dummies provide valuable information on the
annual movements related to technology change and the input variable
?logbed?  represents the proxy for capital. If I leave out logstaff or
logdis (represents discharges) some time dummies drop out and I cannot
calculate anymore any technical efficiency scores for each observation and
year by using 

predict te, te

which is quite important for me as I am focusing on technical efficiency
measurement.

Thanks in advance for your help.  Any advice on this issue is highly
appreciated.
Kerstin




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