It's important to note that in the 2006 study that Caplan cites, which reported that 18% of social scientists identified as Marxists, the other options offered

It's important to note that in the 2006 study that Caplan cites, which reported that 18% of social scientists identified as Marxists, the other options offered were all about political affiliation rather than economic views (although there is certainly significant overlap between these categories). The prevalence of self-identified Marxists in social sciences, particuarly sociology, may reflect the important role Marx's commentaries on the social outcomes of 19th century capitalism has had in areas like history, sociology, and cultural studies, rather than a commitment to communist economic structures. There are plenty of Marxist scholars who use Marx's methods of analyzing social phenomena without subscribing to his statements about the inevitable triumph of socialism. Marx is generally recognized as a better diagnostician than a prescriptionist, and for fields involved in critical analysis of social-political-economic phenomena it is not surprising to see people who identify (politically) with his work and world view.