Pershing Square hedge fund manager Bill Ackman highlighted prison operator Corrections Corp. as one of the best real-estate businesses around, during a presentation at the Value Investing Congress in New York on Tuesday. The government is a major customer and there is strong demand for prison space and limited supply, Ackman explained. “It’s also a hedge against your hedge fund business, because as the SEC ramps up…” Ackman said, prompting laughter at the conference. “We shouldn’t joke about that,” he added.