Lopsided left representation among U.S. college faculties is well known. Dan Klein and Charlotta Stern sum it up in "Narrow-Tent Democrats and Fringe Others: The Policy Views of Social Science Professors."
Their survey finds that academic economists are 3:1 left, political scientists almost 6:1, historians 8.5:1, political and legal philosphers 9:1 and anthropologists and sociologists 21:1.
They also find that both groups lean to statist views.
Paul Krugman had once explained this state of affairs with the suggestion that conservatives are too dumb to serve on decent faculties.
Many have commented on the subtle and the not-so-subtle screenings that are at play in many academic units. A variety of research specialities and topics are code for politically correct and this often gives applicants a leg up.
But what animates the process? Many people are happier to be surrounded by like-minded colleagues that reinforce their world view -- in spite of the diversity mantra. And many others, to their great discredit, probably believe that Krugman is right.