It is well-known by now that the number of women in college exceeds the number of men. The question is why. In a new NBER working paper, Claudia Goldin, Lawrence Katz, and Ilyana Kuziemko try to figure out if it's an increase in the demand for college degrees by female students, or perhaps an increase in the supply of college-educable females.

There are many demand-pull factors, including delayed marriage, increased female labor participation, and the "pill". The authors note that "the jury is still out concerning whether the full lifetime economic returns to college are greater for women than for men," but that the wage premium for college degrees for females is greater than that for males.

More surprising to me, however, is that the supply of males eligible for college might be dropping relative to that for females. In the paper itself (link for NBER subscribers only) :

Jacob (2002) finds, using the NELS, a much higher incidence of school disciplinary and behavior problems for boys than girls and a far lower number of hours spent doing homework for boys than girls. Controlling for these non-cognitive behavioral factors can explain virtually the entire female advantage in college attendance for the high school graduating class of 1992, after adjusting for family background, test scores, and high school achievement. Similarly, we find that teenage boys, both in the early 1980s and late 1990s, had a higher (self-reported) incidence of arrests and school suspension than teenage girls, and that measures of behavioral problems significantly attenuate the female college advantage. Reinforcing these findings is evidence that boys have two to three times the rate of Attention Deficit Hyperactivity Disorder (ADHD) than girls and much higher rates of criminal activity (Cuffe, Moore, and McKeown 2003; Federal Bureau of Investigation 2004). Boys are also much more likely than girls to end up in special education programs. The source of boys� higher incidence of behavioral problems is an area of active research and could be due to their later maturation as well as their higher rates of impatience (Silverman 2003). Because gender differences in development and behavior are not unique to any particular country, they can explain why the reversal of the gender gap in college has occurred throughout much of the developed world once female access to college and to labor market opportunities were improved.

So perhaps the cost of the 'war against boys' can now be measured. As Christina Hoff Sommers pointed out last year, it may be that the supply of female students to college is higher now because the education establishment finds it easier (or more desirable?) to generate a female college-prepared high school graduate than a male one.