Paul Krugman’s failed attempt to excuse the academy’s liberal bias is a very good sign. A spate of studies documenting campus bias, the Summers and Churchill fiascos, and the rebellion of students tired of one-sided education, have combined to put the academy under real pressure. Liberals now have to defend the indefensible, whereas before they could simply ignore the problem altogether. The fact that Krugman has to begin with an admission that professors are overwhelmingly liberal is progress.

Krugman argues that the political bias of professors is explained by self-selection. That’s a joke. As any aspiring conservative academic knows, the radical faculty carefully polices new hires for politics. Most conservatives have to hide their views to have any chance at all. Unfortunately, in today’s academy, the substance of academic work is so politicized that there’s no easy way to hide. Failing to be openly radical is often enough to do you in. Whole fields (and therefore many job searches) are actually defined by politics–post-colonial studies, for example. To see how academic bias really works, check out this great article from The Chronicle of Higher Education by Mark Bauerlein.

You can see the effect of politically biased hiring in the numbers. As Howard Kurtz reports, only 39 percent of professors in 1984 described themselves as liberal. The current figure is 72 percent. And, of course, by 1984, the march of the tenured radicals through the groves of academe was already well underway. The culture wars kicked off by William Bennett and Allan Bloom’s response to the new campus radicalism began around 1986. Krugman’s self-selection theory can’t explain this huge jump in the percentage of liberal professors over time. If liberals are more attracted to the academic life than conservatives, the effect over time should be constant. A study reported on by John Tierney in 2004 also showed a huge jump in campus liberalism over time. Democratic professors now outnumber Republicans by at least seven to one in the humanities and social sciences–a ratio more than twice as lopsided as it was three decades before. This shift is the result of deliberate political bias, not of some supposed affinity of liberals for the campus life.

Not only does Krugman ignore the shift over time, he downplays the differences between disciplines. The latest study showed that business, engineering, and economics faculties were 49, 51, and 55 percent liberal, respectively. English literature is 88 percent liberal. This disparity has nothing to do with liberal love of the academic life, and everything to do with politics. Yes, as Krugman points out, even many scientists are liberal. Krugman says that’s because scientists hate religious Republicans. I think it’s far more likely that we have here a politically based self-selection effect here. Imagine that you’re a conservative with an interest in science. You have a choice between doing research for a business, or living on a college campus. Which would you choose? Look what happened to Lawrence Summers. Any scientist or engineer with a conservative bent knows he’d be a fish out of water in a campus culture controlled by the radical left. That, if anywhere, is where self-selection is at work.