KK,
I actually saw that definition when I googled Santorum. Funny!
Read the book "Freakonomics", and one of the ideas they explored was what effect abortions had on the crime rate.
Apparently homocide rates in teens had been steadly increasing over time and they were concerned that in the early 90's it would spiral out of control.
Levitt proposed that the increase in abortions in teh early 70's did away with unwanted children, and that possibly these unwanted children would have contributed to the increasing trend of teen homocides.
I don't either agree, nor disagree with Levitt. I find his conclusion interesting. Other economists have had issues with his finding, as well. But then again, economics is part science, and part guesswork.
I would say that increasing longevity and lower death rates would be more of a contributor to lower amounts of funds, as would higher unemployment in recent years, and underemployment (lower average incomes for those still working), which leads to lower contributions of workers over time. To place the blame squarely on abortion is pretty whacky. It might explain once part of the projected funding over time, but there are many factors that need to be weighed, not just one.
Unfortunately in life, there are few contants, except for change.