Here are some interesting facts and figures from the U.S. Census Bureau:
*Women who live in metropolitan areas and are affluent are more likely to be childless.
*More than 47 percent of women who make more than $75,000 a year have no children.
*40 percent of those who make less than $20,000 are childless.
*More than 50 percent of Asian-American women are childless.
*Latinas are the most likely ethnic group to have children.
I would have to make an Darwinian assumption that smarter (or more aggressive) women are breeding (or not breeding) themselves out. Of course it’s a pretty assumption, but it does say affluent and 75 thousand plus.