Here’s the abstract from that Science paper. I think it best lays out the situation.

Examination of aggregate data on graduate admissions to the University of California, Berkeley, for fall 1973 shows a clear but misleading pattern of bias against female applicants. Examination of the disaggregated data reveals few decision-making units that show statistically significant departures from expected frequencies of female admissions, and about as many units appear to favor women as to favor men. If the data are properly pooled, taking into account the autonomy of departmental decision making, thus correcting for the tendency of women to apply to graduate departments that are more difficult for applicants of either sex to enter, there is a small but statistically significant bias in favor of women. The graduate departments that are easier to enter tend to be those that require more mathematics in the undergraduate preparatory curriculum. The bias in the aggregated data stems not from any pattern of discrimination on the part of admissions committees, which seem quite fair on the whole, but apparently from prior screening at earlier levels of the educational system. Women are shunted by their socialization and education toward fields of graduate study that are generally more crowded, less productive of completed degrees, and less well funded, and that frequently offer poorer professional employment prospects.

Bickel, P. J., Hammel, E. A., and O’Connell, J. W. (1975) Sex bias in graduate admissions: Data from Berkeley. Science, 187, 398–403. [PDF]

Note that “selective” also means “popular”, since departments with many applicants can pick and choose exactly who they want to admit. In other words, the departments where women dominate are the popular departments, like English, Psychology and Sociology. The departments where men tend to dominate are the less popular ones, like engineering, etc.

A much higher percentage of English, Psychology, and Sociology students apply to grad school than engineering, math, etc, students because once they graduate they realize that a B.A. in whatever they have is worthless, and they need a better degree. That and there are more of them as undergrads to apply. Couple that with the fact that there is a significant enrollment bias of women in English, Psychology, and Sociology compared to men. It is to be expected that more women are in the popular grad programs simply because more apply.

Also, none of this is surprising, since schools force their acceptance rates to be equal for each gender. They do not take the best (for example) 10% of their candidates, they just take the 10% best candidates for each gender, lest they be sued. It’s quite sad that we can’t just choose the best.

BTW, For many more cool mosaic plots, and others, see Michael Friendly’s home page http://www.math.yorku.ca/SCS/friendly.html