Private equity claims to be adept at revamping beleaguered businesses. But who will clear up the industry's own group of stragglers? Firms dogged by poor performance have been shut out of raising money for several years, surviving on management fees and the hope that economic recovery will bail out troubled portfolios. Investors have limited options to speed up change.

So-called tail-end or zombie funds, where the manager's track record will preclude raising more cash, could total $500bn, according to Triago. And 60% of US and European buyout firms closed their latest fund in 2008 or earlier, with half yet to even attempt a new fundraising round, according to Bain & Company. That suggests that the sector is ripe for a shake-up.