Statalist


[Date Prev][Date Next][Thread Prev][Thread Next][Date index][Thread index]

st: RE: xttobit initial value not feasible


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: xttobit initial value not feasible
Date   Mon, 14 Apr 2008 17:31:32 +0100

Consider a standard regression of your response (call it y) on any two
predictors. 
Then a simplified analogue of your problem is that two-thirds of your
data lie on
the plane y = 0 and the other third lies on one side of that plane.
Geometrically that sounds 
a pretty awkward situation to model. Having more predictors and using
tobit don't I think 
make it any easier. 

There is no positive suggestion embedded here, just a thought that the
message doesn't sound that 
surprising in such a light. 

Nick
n.j.cox@durham.ac.uk 

sarah young

I have been trying to run xttobit without success. The problem is
"initial value not feasible".

I have a panel of more than 4000 firms for 15 years, which altoghther
is about 62,000 firm-year observations. The dependent variable is
export intensity, two thirds of which are zeros. So I chose to use
Tobit model. The model is on the determinants of export intensity,
theoretically the choosing of the independent variables is fine, which
include TFP, age, size, R&D intensity etc, as well as year and
industry dummies. I have tried by using different sets of independent
variables, for example, including only one variable on the right side,
excluding year and industry dummies, all of these not working and the
message was the same, "initial value not feasible."

I have searched on Statalist archive and found this thread:
http://www.stata.com/statalist/archive/2007-05/msg01036.html

I tried to solve the problem according to the suggestions in the
thread but still it is not working. Could anyone give some advice?
What are the possible problems behind this? How to solve them?

*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/



© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   What's new   |   Site index