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Re: st: zero inflated poisson (zip)

From   Maarten Buis <>
Subject   Re: st: zero inflated poisson (zip)
Date   Tue, 17 May 2011 10:06:49 +0200

On Tue, May 17, 2011 at 9:49 AM, Marie-Claire Robitaille-Blanchet wrote:
> I am using a zero-inflated poisson to estimate a gravity model of bilateral trade.
> * For the poisson-part of the model, the coefficient for the log of distance is: -0.7039
> * For the probit-part of the model, the coefficient for the log of distance is: 0.1549
> I understand how to interpret separately those coefficients but I am wondering if there is any way I can create one comprehensive measure for the total impact of distance on bilateral trade. Any reference?

The zip model implies a expected trade, so the total impact would be
the effect of distance on this expected trade. You can get that by

margins, dydx(distance) predict(n)

For more, see -help margins- in combination with -help zip postestimation-.

Hope this helps,

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