James Lundgren of Northwestern University law school has been studying law faculty diversity since 1997, Measuring Diversity: Law Faculties in 1997 and 2013, and finds that white male Christian Republicans are the most underrepresented:

The data show that in 1997 women and minorities were underrepresented compared to some populations, but Republicans and Christians were usually more underrepresented. For example, by the late 1990s, the proportion of the U.S. population that was neither Republican nor Christian was only 9%, but the majority of law professors (51%) was drawn from that small minority. Further, though women were strongly underrepresented compared to the full-time working population, all of that underrepresentation was among Republican women, who were — and are — almost missing from law teaching.

By some measures, in 1997 the most underrepresented racially defined groups were Non-Hispanic white Republicans and non-Hispanic white Protestants, the latter being pejoratively known as WASPs, the supposed dominant group.

And it has gotten worse, not better:

In an Afterword, I update the race and gender data on law faculty diversity, incorporating the most recent ABA release for the 2013-2014 academic year. The only large racial or gender groups that are now significantly underrepresented compared to the lawyer population of a similar age are non-Hispanic whites, males, and non-Hispanic white males. And by some measures the most overrepresented race and gender groups in law teaching compared to lawyers are minorities combined, African Americans, and females. Affirmative action has succeeded so thoroughly that, compared to lawyers, the largest underrepresented groups in law schools today are white Christians, Christians, white Republicans, and Republicans.

Ideologically, conservatives are almost non-existent:

In terms of absolute numbers, the dominant group in law teaching today remains Democrats, both male and female. Because in the general public both white women and white men tend now to vote Republican, law faculties are probably less representative ideologically than they have been for several decades — a disappointing result after four decades of hiring intended to make law professors more representative of American society.

UCLA law professor Stephen Bainbridge doesn’t think the lack of ideological diversity is the result of affirmative action, but self-selection:

Lindgren opines that these sort of disparities are “too large and too consistent to be simply the result of discrimination,” arguing that “culture probably also plays an important role.”

I used to think that the problem was mostly a network effect issue. While I still think network effects are important, it seems clear that at least unconscious discrimination is at work as well.