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Re: st: xtfrontier tvd

From   Scott Merryman <>
Subject   Re: st: xtfrontier tvd
Date   Fri, 6 May 2011 07:33:10 -0500

Have you tried using the -difficult- option or changing the
maximization technique?
  See -help maximize-


On Thu, May 5, 2011 at 10:39 PM, Apurba Shee <> wrote:
> I am using xtfrontier command to estimate time varying decay model..
> xtfrontier logdvar logindvars, tvd
> I am running this production frontier for data in different sectors.
> For some sectors this is working fine. But for other sectors this
> command is unable to estimate the production frontier parameters and
> showing that the loglikelihood is not concave and the iterations go on
> forever. This is happening for a lot of dataset. But in these dataset
> time invariant model (xtfrontier, ti) is working fine. I was wondering
> if anyone can address the issue on how to estimate production frontier
> in this situation.  Thanks
> Apurba

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