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Re: st: How to add restriction condition in Stata

From   Raymond <[email protected]>
To   [email protected]
Subject   Re: st: How to add restriction condition in Stata
Date   Fri, 29 Jul 2005 12:05:29 -0400

Actually, I'm using an age-period-cohort model, and I need to put all
the three variables in
the model. Without restrictions, there will be an identification
problem since cohort=period-age.
Thanks for your suggestions. I'll try it.

On 7/29/05, Richard Williams <[email protected]> wrote:
> At 11:51 AM 7/29/2005 -0400, Raymond wrote:
> >Thanks!
> >But the reason I make coeffients of age1 and age2 be equal is to solve
> >an identification
> >problem. So, I cann't just sum them up.
> I'm not sure how you are getting an identification problem in a poisson
> regression or how setting the effects for 2 dummies equal solves it.  Maybe
> you should write out your model.  But in any event, I think the test
> command I gave before will still work; and the poisson command does support
> constraints, so you could do
> constraint 1 age1=age2
> poisson y age1 age2, constraints(1)
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