Larry Summers thinks about it:
The Liberal (and Moderating) Professoriate: Summers said he identified strongly as a liberal and a Democrat, but that while in Washington he viewed himself as being on “the right half of the left,” in Cambridge, he landed “on the right half of the right.”... Summers said, he found “even less ideological diversity” than he thought he would, and that in the humanities and social sciences, Republicans are “the third group,” after Democrats and Nader and other left-wing third parties.
To date, Summers said, he has largely viewed the political imbalance as one of “able people making choices.” He said that if you are a smart individual, and you like the market, profits, and “striving for profits,” you have “a wide range of choices in life,” of which an academic career is but one. If you are a smart person who doesn’t like the world of markets and profits, “you have a much narrower range of choices,” he said, and academic careers may be quite desirable. In this way of thinking, he said, it’s not surprising to find more liberals than conservatives on college faculties.
At the same time, he added, the extent of the imbalance and some informal research he has conducted “give me pause”.... It’s not that there are no conservative professors, he said, but their share is so small as to raise questions that deserve more attention. Summers wondered if the situation isn’t like it was in the early days of baseball’s racial integration, when people trying to say equality had arrived could point to the relatively equal performance of black and white stars. “But it appeared that there were not any African-American 0.250 hitters,” Summers said. “The only [black] players who played were stars.”
Summers said it would be “extraordinarily unwise and dangerous” for government to try to force more balance in hiring. And he said it would be “a real horror” if, in the name of respecting all views, Harvard’s astronomy department hired an astrologer or the biology department hired a creationist. But while there is a “tension” in calling for more diversity of views, while excluding views such as those, he said it was worthy to seek more ideological diversity.
One reason... is to help liberalism. “As someone who is a strong Democrat and is a liberal, and does not think that we have won the argument with the country over the last 40 years, rather to the contrary, it makes me wonder whether if you do not engage in intense dialogue with those whom you disagree with in substantial number whether your own arguments will be sharpened and honed to maximum effect,” Summers said....
There is another argument for saying that more ideological balance in higher education shouldn’t be a goal, Summers said, and it is one that he understands, but questions. This perspective relates to conservative success in much of American society. “From the perspective of many, they’ve got the White House, the Supreme Court, the CEO’s of 85 percent of the Fortune 500. They’ve got Fox News. They’ve got an increasing share of the media, so is the right way to have diversity to change the one thing that’s progressive?” While Summers said that this attitude creates “a problematic role for universities to put themselves in,” he said that it explains the “extreme hostility” of some in academe to conservative ideas.
From where I sit, I don't think that either economics or political science has a conservative problem--meaning that I find myself slightly on the left as far as both disciplines are concerned. And I don't think any institution anywhere has a too-few-Republicans problem: universities don't need more believers in intelligent design or the appicability of the Laffer curve or the unitary executive or the genetic inferiority of Africans or more disbelievers in global warming. Do other disciplines have a too-few-conservatives problem? Perhaps, but I don't think it can be solved: I cannot think of a sociology department that would be improved by hiring Charles Murray or a philosophy department that would be improved by hiring William Kristol or a Middle Eastern studies department that would be improved by hiring Daniel Pipes. Perhaps there are history departments that would be improved by Ronald Radosh, perhaps not. But anti-meritocratic discrimination against thoughtful conservatives should create an opportunity and an obvious pool of potential high-quality conservative hires. I don't see such a pool anywhere.