A massive rally in the equity markets since May bringing in heavy inflows into equity ETFs and open-ended debt funds has helped mutual fund AUM grow 17 per cent to top the Rs 31-lakh-crore-mark in 2020, which is 1 percentage point lower than 2019, according to a report. During the year, the 44-player industry has added Rs 4.5 lakh crore to the AUM, while in 2019 it grew 18 per cent from Rs 22.86 lakh crore in 2018, when it had grown only 7.5 per cent, as per Crisil data.