(The Wall Street Journal) -- Private equity firms say they are experts at wringing profits out of flagging businesses. It turns out they are almost twice as good at wringing fees out of their investors.

This finding -- part of a study by two professors at the University of Pennsylvania's Wharton School -- upends one of the deepest-held notions about the buyout business: The bulk of the average private equity firm's earnings come from profitably refashioning and reselling the businesses it buys.