In general, women as a group were younger than male faculty. Women are more recent entrants into academia than men, therefore women’s representation among academic faculty was conditioned not only on the number of new Ph. D.s being granted to women, but also on the initial age and sex composition of faculty members and changes in the number of faculty positions (Hargens and Long, 2002). Moreover, “while new cohorts of Ph. D.s entering the academic market­place are increasingly female, each new cohort is only a small proportion of those currently employed. Consequently, the move toward parity in the representation of women must occur slowly” (NRC, 2001:132). Hopkins (2006:16) gave an example in the case of MIT:

In part, the small number of women faculty in [the Schools of] Science and En­gineering can be explained by (1) the fact that the “pipeline” began to fill only about 40 years ago; and (2) faculty turnover rates are slow, with many faculty who achieve tenure staying at MIT for 30-40 years. Only about 5% of the MIT faculty leaves each year due to retirement, failure to achieve tenure, or other fac­tors. At this rate, and assuming a 50% tenure rate, it would take approximately 40 years for a department that had no women faculty to have a faculty that has the same percentage of women as the Ph. D. pool.

As the NSF (1999:99) notes: “many of the differences in employment charac­teristics between men and women are partially due to differences in age. Women in the science and engineering workforce are younger, on average, than men: 18 percent of women and 12 percent of men employed as scientists and engineers were younger than age 30 in 1995.” Since women faculty are younger, they have had, on average, less opportunity to receive tenure or a promotion, making career age a vitally important factor to control for in assessments of gender disparities in rank and tenure status (see e. g., NRC, 2001a; Olson, 2002).