So by "very large subpopulation who aren't really capable of using birth control effectively", what you meant to say that "people who report using condoms alone

So by "very large subpopulation who aren't really capable of using birth control effectively", what you meant to say that "people who report using condoms alone for birth control only have an 85% success rate?" Which in turn you are using to prove that "unstable sexual relationships through the peak reproductive years mean you're likely to end up with children"? I think that you may wish to reinvestigate your original point.