[Limdep Nlogit List] Stochastic Cost frontier Error query

William Greene wgreene at stern.nyu.edu
Thu May 15 00:13:04 EST 2008


Barry.  This is a model misspecification problem.  I would start with
a Cobb-Douglas with nothing else in it, and build it up a variable at
a time. You will discover that one of your variables is the problem, 
and then you can look more closely and discern why that is the case.
/B. Greene

----- Original Message -----
From: "Barry Quinn" <bquinn14 at qub.ac.uk>
To: limdep at limdep.itls.usyd.edu.au
Sent: Wednesday, May 14, 2008 9:02:35 AM (GMT-0500) America/Bogota
Subject: [Limdep Nlogit List] Stochastic Cost frontier Error query

Hi,

 

I have been using Limdep to run a translog stochastic cost frontier with the
default model setting.  My specification includes 25 regressors and I have a
small sample (419 observation).  I have also normalised all variables about
their mean to encompass an expansion point aspect.

 

The following message appear 

 

Error   143: Models - estimated variance matrix of estimates is singular

 

Is  this likely to be a model misspecification issue ??

 

Barry Quinn

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-- 
Professor William Greene
Department of Economics
Stern School of Business
New York University
44 West 4th St., Rm. 7-78
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http://www.stern.nyu.edu/~wgreene
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