The top five investment banks are set to clean up in equities with margins of 15% to 20%, leaving only a few scraps and making life “very difficult” for mid-tier firms with global ambitions, according to Morgan Stanley and Oliver Wyman.

Unlike some other areas such as foreign exchange and fixed income trading, only a handful of banks and boutique firms in cash equities will flourish. "In equities the barbell structure makes the economics very difficult for mid-tier firms, carrying the full cost structure of the platform," the report said.