I would hazard to guess that is related to two factors: women are the largest group that are underrepresented; and it is harder to explain women's underrepresen

I would hazard to guess that is related to two factors: women are the largest group that are underrepresented; and it is harder to explain women's underrepresentation as a result of socio-economic factors. No matter where you live, you can expect women to represent ~50% of the population. That makes it very easy to notice if there is a discrepancy, even if you work in a tiny office. To tell whether an ethnic/age group is, you first need to know the prevalence, then you need to have enough people that a discrepency is noticeable. With a number of groups you can explain why a group is underrepresented by looking at socio-economic factors like their average income, access to technology, access to schooling, etc. For any socio-economic group, there should be (roughly) the same number of men and women in that group, so it can't be used as an explanation of the under-representation of women. EDIT: I didn't notice that jailbot had already said what I said, but in a less wordy fashion.