Jonah pointed me to this artice, The '60s Begin to Fade as Liberal Professors Retire, which chronicles the shift toward political moderation among the professoriate. That moderation seems to be less about changes in views toward the center of the American political distribution than it is a greater focus on career as opposed to striking a pose as a social revolutionary. As it happens, you can find the working paper which has most of the data which the article is based on, THE SOCIAL AND POLITICAL VIEWS OF AMERICAN PROFESSORS. Below the fold I've placed the most interesting graphs, where you can see one which shows that the majority of professors ascribe the underrepresentation of females in science & engineering not to discrimination (about 40% of professors are female).