[Limdep Nlogit List] Heckit model

[Randy Kesselring]

Marc,

When you run the probit, it uses all of your observations and you have a
sufficient number to accomplish that estimation.  When you use the
select command it selects only the observations for the variable on the
left-hand-side of the probit that equal one.  This significantly reduces
the number of observations, and in your case, there are not enough
observations to accomplish the estimation.

Randall G. Kesselring
Professor of Economics
Arkansas State University
Phone: 870-680-8467
Randyk at astate.edu
-----Original Message-----
From: limdep-bounces at limdep.itls.usyd.edu.au
[mailto:limdep-bounces at limdep.itls.usyd.edu.au] On Behalf Of Marc
Goergen
Sent: Friday, November 30, 2007 1:44 PM
To: limdep at limdep.itls.usyd.edu.au
Subject: [Limdep Nlogit List] Heckit model

Dear all

I am trying to run a Heckman selection model. The probit runs well, but
when
I try to run the linear regression using the 'select' command I get
"error
message 201: SELECT - selection leaves insufficient degrees of freedom".
What is the cause of this?

Best wishes,

Marc 



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