When you get around to building a statistical model, make sure you take into account that vasecotomies cost about 1/4 as much to perform (e.g. $700 vs $2800, in the US), and have are something like 20x less likely to have complications (although complication rates are low for both).
It would be cheaper to do IUDs than tubal ligation for women. There was a bill that proposed this in Arkansas, but it was shot down for being coercive.
I think that the argument from "avoiding coercion" is silly. First, because that isn't what literal coercion means. But moreover, At federal minimum wage, that money only takes 350 hours to earn. Over 18 years, thats 20 hours a year. If someone doesn't value being a parent enough to work an extra 23 minutes a week, then it doesn't seem like that is a right they value particularly highly. Also, there are laws that, taken together, coerce parents into working more than 23 minutes a week to support and care for their children. If we aren't willing to get rid of laws against child neglect, why are we worried about coercion in this case?
source: http://www.ncbi.nlm.nih.gov/pubmed/19041435