A recurrent question regarding the dominance of left/liberal perspectives among university professors is the extent to which this lopsidedness arises from discrimation against those with non-left viewpoints that excludes them from the academy versus self-selection by conservatives and libertarians out of academia and into other professions, such as law and business.

The issue has arisen again in light of a new study by Woesner and Kelly-Woessner "Left Pipeline: Why Conservatives Don't Get Doctorates." The paper is a chapter in a forthcoming book by the American Enterprise Institute on "Reforming the Politically Correct University." The papers from the conference are available here. I've read a number of the papers posted there and they are very interesting.

The paper is also discussed on The Economist's Voice here.

There is also a story in the Chronicle of Higher Education on the study here.

Dan Klein, who has written extensively on this issue, has written up a comment on the Chronicle story that he has asked me to post on his behalf (I do so below). Dan raises one concern that I share about the study. It is difficult to sort out the self-selection from discrimination hypotheses because the decisions on what subject to study will be shaped at least in part by one's perception about the likelihood of success in a given area of study. Thus, for instance, if a scholar perceives that one occupation will subject her to discrimination that will limit her career accomplishments while another would not, then at the margin many are going to pursue the one where that is not the case. And, in fact, prior studies have found that the ideological disparity is greatest in those fields with the most subjective standards (such as English and History) and the gap is narrowest in those fields such as economics and sciences that are generally perceived as less subjective. I have also seen it asserted (although I can't find the discussion right now) that within political science itself those who do use more formal modeling and quantitative methodologies is much more equal in ideological orientation than those who use "softer" techniques.

Dan's primary point of emphasis in his comment, as I understand it, is that this data on the self-seleciton hypothesis doesn't account for his finding that among those who have already received their PhD "conservatives" are more likely to end up outside academia than liberals. So that, for instance, taking the pool of those who have already received a PhD in History, those who are conservative are less likely to hold an academic position than a similarly-situated liberal. Such disparities, Klein argues, are unlikely to reflect self-selection because those who pursue a PhD in History (for instance) have implicitly manifested an interest in being a professor, regardless of ideological orientation.

Since Dan doesn't have his own blog and in the interest of getting his argument out there for debate I reproduce his full comment on the Chronicle story. With respect to Dan's negative view of the Chronicle, I don't read it very much so I don't express any independent view on whether I agree with his opinions. I do, however, certainly share Dan's view that Inside Higher Ed is far more independent of the higher education establishment than the Chronicle and is much more insightful in its coverage. Here's Dan's comment (it is fairly long, so I've placed a good portion of it under hidden text)

Deleted at Daniel Klein's request. See explanation here.