The percentage of women 40 to 44, those at the end of their childbearing years, who have not given birth has hovered around 18 percent since 1994, but that's up from 10 percent in 1976.

Non-high school graduates and those with bachelor's degrees were most likely to be childless. Also women with higher incomes had the highest childless rates, in part a reflection of the increased professional options available to them, said David Popenoe, co-director of the National Marriage Project, a research group at Rutgers University.

KTAR David Leibowitz asked on his show today if this was a sign of selfishness on their (and spouse) parts?