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Re: st: Interdependent panel system


From   "Austin Nichols" <austinnichols@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Interdependent panel system
Date   Thu, 4 Sep 2008 10:54:33 -0400

As written, p is not endogenous in eqn (2), but it should be, since p
and q are determined by the intersection of supply and demand curves
both shifted by various factors over time, and no, -xtreg- is not
sufficient--you should find an instrument and use -xtivreg2- (

ssc inst xtivreg2
ssc inst ivreg2
ssc inst ranktest
etc.

) to estimate eqn (2). For details, read the help file for -ivreg2-
and its refs.

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On Thu, Sep 4, 2008 at 5:48 AM,  <JensMehrhoff@web.de> wrote:
> Hello everyone,
>
> I have a small N,  large T panel data set and I would like to estimate the price elasticity of demand.
>
> My system reads:
>
> (1) p(i,t) = a0(i) + a1*p(i,t-1) + u(i,t)
> (2) q(i,t) = b0(i) + b1*p(i,t) + v(i,t)
>
> Hence, my question is: Which estimation procedure is appropriate, given that p(i,t) is endogeneous in equation (2) and depends on its own lag in equation (1)? Furthermore, are standard panel techniques applicable - my panel is NOT large N, small T but vice versa?
>
> I'm only interested in the parameter b1 (variables are in logs, thus b1 is the price elasticity of demand). Can I estimate (2) without respect to the endogeneity of p(i,t) with say xtreg?
>
> Many thanks in advance for your comments!
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