With the jails filling up with his colleagues, William Ackman has decided to invest in incarceration.

Ackman’s activist hedge fund shop, Pershing Square Asset Management, has taken a 9.5% stake in private prison company Corrections Corp. of America (CXW). While Ackman joked that it's a “hedge against your hedge fund business… as the SEC ramps up” its investigations into the industry, he told the Value Investing Congress that his investment had less to do with reforming criminals and more to do with real estate.