Dear Statalist colleagues,
I would like to estimate the following regression:
BD=aX+bS+e
where BD=birth defect and S is a measure of smoking (either 0/1 or number of
cigarettes). I would like to instrument S with cigarette prices and other
variables (local
smoking policy variables, eg). The problem, I think, is that > 50% of
respondents didn't
smoke. Does affect the appropriateness of the IV approach? Ie, can my 1st
stage
regression:
S = cZ+dP+e
be estimated if >50% of S is zero?
Any help would be greatly appreciated.
Thanks,
Michael
________________________________________
Michael Ganz, MS, PhD
Assistant Professor
Dept. of Society, Human Development and Health
Harvard School of Public Health
[email protected]
http://www.hsph.harvard.edu/faculty/ganz
Ph. 617-432-2382
Fax 617-432-3755
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