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Re: st: Is it necessary to have some variable for exposure in xtnbreg


From   Steve Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Is it necessary to have some variable for exposure in xtnbreg
Date   Wed, 15 Sep 2010 09:00:02 -0400

--
An exposure variable is an option, not a requirement.

Steve

Steven J. Samuels
sjsamuels@gmail.com
18 Cantine's Island
Saugerties NY 12477
USA
Voice: 845-246-0774
Fax:    206-202-4783

On Tue, Sep 14, 2010 at 8:33 PM, Indu Khurana <indu.statauser@gmail.com> wrote:
> Dear Statalisters,
>
> I have a count data on number of patents which is the dependent
> variable (panel setting). Right hand side variables include Employee
> well being and debt-equity ratio. The data on patents has a lot of
> zeros. Although ZINB could have been an option but I am using fixed
> effects. Therefore I decided to settle with negative binomial, fixed
> effects - xtnbreg
>
> My question is: Is it necessary to have some variable for exposure in xtnbreg?
>
> The data is on 5000 firms for 5 years which all came into existence at
> the same time in 2004. So basically they all have the same exposure.
> And there is no information on month of the the year.
> There is no other time dimension which can be used to fit in exposure.
>
> I was thinking of the following options:
>  1. To ignore exposure variable all together
>      Which I am not sure of whether it is correct.
> 2. To include number of years of owner's education to fill as exposure.
>
>
>
> Please suggest.
>
> Thanks
>
> Indu Khurana
>
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