Chronicle:

The Woessners have peered into the psyche of conservative undergraduates to find out why so few of them want to earn Ph.D.’s and become professors. Their paper on the topic, “Left Pipeline: Why Conservatives Don’t Get Doctorates,” is available online and will be published as part of a book published in August by the American Enterprise Institute.
The Woessners found that liberal students have values and interests that point them to careers in academe, while most conservative students do not.
“The personal priorities of those on the left,” the Woessners conclude, “are more compatible with pursuing a Ph.D.”