Assets under management (AUM) of retail investors putting money through the mutual fund (MF) route topped Rs 20 trillion for the first time, in August. Also, retail investors now account for more than half of the MF industry assets. Until August, the average retail AUMstood at Rs 20 trillion — 50.6 per cent of the industry AUM of Rs 39.5 trillion, data provided by industry body Amfi showed.