The Chronicle of Higher Education, March 9, 2011 by Mary Ann Mason
http://chronicle.com/article/The-Pyramid-Problem/126614/
Put simply: There are far fewer women than men at the top of the academic hierarchy; those women are paid somewhat less than men, and they are much less likely then men to have had children. At the bottom of the academic hierarchy—in the adjunct and part-time positions—there are far more women than men, and they are disproportionately women with children. Women in adjunct jobs have children at the same rate as men but receive the lowest wages in academe.