It's been shown in several studies that political views vary with how much education you have had. People who have a post-graduate degree of any kind tend to be to the left of people who have only a high school or college degree. In the 2004 US presidential election, for example, people with only a high school or college degree voted about 53-46 for Bush, the Republican, whereas people with a post-graduate degree voted 55-44 for Kerry, the Democrat. Indeed, I do not have access to the numbers, but if you focus on people with PhDs, as opposed to doctors (MDs, DDs, etc), lawyers (JDs), and business school types (MBAs), then the difference is even more dramatic. Since philosophers do tend to have PhDs, then, of course they trend with that group.

Does education make you more leftist? Or do people inclined to be more leftist just seek more education? These are interesting questions, but, obviously, they are empirical questions, so I will not try to answer them.