From the WSJ piece Isn't It Romantic? Feminism's latest triumph: Boys are afraid of girls.:
Schalet's most interesting assertion is that "the American boys I interviewed seemed more nervous about the consequences of sex than American girls." … The 2002 National Survey of Family Growth found that more than one-third of teenage boys, but only one-quarter of teenage girls, cited wanting to avoid pregnancy or disease as the main reason they had not yet had sex
The piece also gets into some of the consequences of this - largely parallel to those of Japan's so-called "herbivores". Basically they're not having children, resulting in the sort of problems associated with aging societies, and they're not particularly economically productive either. As a related article, Teenage Boy: Broken Condom Means ‘I could be screwed for the rest of my life’, outlines, this shift is more or less the logical result of the shift in policy over the last fifty years or so.
What else do you find? Here's a bit of an NYT Economix post entitled Young Women Are More Career-Driven Than Men:
Using poll data collected in 2010 and 2011, Pew found that 66 percent of women 18 to 34 years old said that being successful in a high-paying career or profession was “one of the most important things” or “very important” in their lives. Among their male counterparts, the share was 59 percent. This is a reversal from the last time Pew looked at this question, in 1997. Then, young men were more likely to say they prioritized careers than young women were.
... In 1997, 41 percent of men 35 to 64 years old said success in a high-paying career was important to them, compared with just 26 percent of women their age. Today, middle-age women’s professional ambitions have caught up to men’s, with 42 percent of women and 43 percent of men emphasizing their jobs.
So men are more scared of making a woman pregnant than the women themselves are and women say are more likely to speak of placing a higher priority on their careers than men are. It's a strange world.
