"Three board members of SLM Corp. recently made the first insider stock purchases in a year and a half at the student-loan company, known as Sallie Mae, but much of that buying apparently helped to fulfill company stock-ownership guidelines," The Wall Street Journal reports. "All three insiders joined the company this year, and two of them hadn't yet met stock-ownership guidelines set by Sallie Mae before their recent purchases. For those reasons, and because of the company's longstanding issues, the purchases send only 'a slightly positive signal,' Mr. Silverman said. Shares of SLM have lost more than half of their value since the last insider purchase amid a tightening credit environment, cuts in federal subsidies and a failed buyout of the company by a group of investors led by private-equity firm J.C. Flowers & Co. Sallie Mae shares rose 67 cents to $22.94 in 4 p.m. New York Stock Exchange composite trading Tuesday."