One of the oldest and best-known hedge fund strategies has suffered nearly $150bn in client withdrawals over the past five years, as investors tire of their inability to capitalise on bull markets or protect them during downturns. So-called equity long-short funds, which try to buy stocks likely to do well and bet against names set to perform poorly, have underperformed the US stock market in nine out of the past 10 years, according to Nasdaq eVestment, after failing to adapt to markets largely dominated by central banks.