# st: calculating longitudinal-latitudinal distances

 From Scott Cunningham <[email protected]> To [email protected] Subject st: calculating longitudinal-latitudinal distances Date Thu, 20 Apr 2006 11:10:17 -0400

I am currently working on a project wherein I attempt to determine whether abortion restrictions (specifically, state-level laws requiring parental involvement for minors seeking an abortion and mandatory delays for all women seeking abortions) affects sexual debut and contemporaneous sexual frequency (as well as contraception decisions). To do this project correctly, I have to control for the distance between a woman in my sample affected by the law (ie, a minor in a state with an parental involvement law, and all women for the mandatory delay law) woman's proximity to an out-of-state abortion provider (ie, in a state without the law). The idea is that the law is not binding if a woman can travel out-of-state to elect an abortion.

I know the formula for calculating distances using latitude/ longitude, but am having trouble thinking of the most efficient way to do this in Stata. My problem requires that I find not the distance between every county and every abortion provider, but rather, every county where I have a respondent living and assuming they live in a state with a binding abortion restriction law, the distance from their county and the nearest abortion provider without the law. If they don't live in such a state, then I need only to indicate the distance from their county of residence and the nearest abortion provider at all.

So, my question is not about the mathematical formula for calculating geographic distance, but the most efficient way to do this in Stata. Does anyone have any insights to help me think through this?

scott
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