I know it sounds crazy, but the Protagonist at Wyatt's Torch is onto something.  As a solution to the abortion (and social security) problem, he proposes what he calls a Maternal Lien, in which a child at the age of 21 becomes liable to a debt of, say, $20,000, which he pays back over time.  This would encourage mothers not to abort their children, assuming the system somehow replaced Social Security.
I can't see it ever happening, but it is definitely reminiscent of older cultures (including Biblical Jewish culture) in which children are responsible for the care of their parents, particularly the mother.

I discussed this idea with my parents, and they pointed out that the concept is not Biblical in the purest sense, since younger women should be able to provide themselves with some sort of income, and all women--young and old--who are married should be provided for by their husbands.  Also, parents in Jewish culture were expected to build up and save an inheritance for their children.  In other words, the parents save for the kids, then the kids take care of the parents in old age.  Beats a nursing home, doesn't it?

So the Maternal Lien concept has some weak spots, but hey, all great ideas start somewhere don't they?  What if the Lien debt didn't kick in until the mother was single and over 60?

I tell you, the Protagonist is onto something.