http://chronicle.com/img/photos/biz/bottomline-45.pngBy Don Troop. President Obama took aim last week at rising levels of student borrowing, but two graduate students in sociology say the real culprit for growing college debt is Wall Street. In a report posted last week on the Web site of the Scholars Strategy Network, Charlie Eaton and Jacob Habinek, doctoral candidates at the University of California at Berkeley, assert that the expanding burden of tuition debt is “partly driven by the indebtedness universities have taken on.” Public research universities have passed along their own debt to students by raising tuition and fees by an average of 56 percent from 2002 to 2010, say the authors, who work in the branch of sociology known as financialization.