Re: st: Mixed Poisson models with degenerate conditional distribution for a given value of a covariate

[Maarten buis <maartenbuis@yahoo.co.uk>]

--- On Wed, 2/3/11, Alexander Limonov wrote:
> I'm working with a count data-generating process where the
> dependent variable is restricted to 0, if one of the
> covariates (let's say it's nonnegative and discrete) is 0.
> This occurs in a nontrivial number of cases. Otherwise, the
> dependent variable may be assumed to follow any conditional
> discrete distribution of your choice, but Poisson could be a
> start.
<snip>
> -Does the ZIP model fit the process I'm describing, and
> what modifications are necessary? 
> 
> -If yes, is there a way to "hack" this together with
> existing Stata procedures? 
> 
> -If no, what model would be appropriate?

Sounds to me similar to a selection model. The classic example
would be the case where we are explaining women's income and
homemakers have no income. -cmp- seems to allow for a wide
range of selection models which could include count models.
You can download that package by typing in Stata 
-ssc install cmp-, a paper explaining it can be found here:
<http://ideas.repec.org/p/cgd/wpaper/168.html>

Hope this helps,
Maarten

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://www.maartenbuis.nl
--------------------------


      

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