[Limdep Nlogit List] Problem with NLSUR

[wgreene at stern.nyu.edu]

Mr. James. Your errors are theoretical, not in the command. (1) if you are going to use instrumental variables and not nonlinear least squares, you don't have enough instruments. You'd need at least 5. (2) you are using the variables in the equation (too few in number) as instruments. This does not make sense.  You are not defining an IV estimator this way. If you just want to use SUR, delete the ;inst=... From the command.
/B. Greene


------Original Message------
From: Rao, James
Sender: limdep-bounces at limdep.itls.usyd.edu.au
To: limdep at limdep.itls.usyd.edu.au
ReplyTo: Limdep and Nlogit Mailing List
Sent: Mar 12, 2009 5:14 PM
Subject: [Limdep Nlogit List] Problem with NLSUR

Dear limdep listers,

Am pretty new to limdep so kindly excuse my silly questions and mistakes. Am
trying to estimate a nonlinear system of equations using the NLSUR command
for NL3SLS exemplified as follows:

NLSUR   ;Lhs = lnY, lnfert_d
        ;Fn1 = a1 + a2*x2 + a3*x3
        ;Fn2 = -Log(a2) + b1*x3 + b2*x4
        ;Labels = a1, a2, a3, b1, b2
        ;Start = 0, 1, 0, 0, 0
        ;Inst = x3, x4$

Whenever I try to run this estimation I get the following error messages
"Error   143: Models - estimated variance matrix of estimates is singular"
"Error   447: Current estimated covariance matrix for slopes is singular"

Where could the mistake be?

=============================================================================
==
Rao E.O. James (Msc)
Research Associate/PhD Student

Department of Agricultural Economics and Rural Development
Georg-August University of Göttingen
Platz der Gottinger Sieben 5
37073 Göttingen, Germany.
 
Tell:+49-551-394443 (Office)
E-mail: jimrao2 at yahoo.co.uk;  James.Rao at agr.uni-goettingen.de

Courage is not the absence of fear but the triumph over it ... so fear not to
fear ... but strive to overcome fear!


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