In a measure of the significance of self-managed super funds as a target market for banks, National Australia Bank briefing documents show that 31 per cent of the turnover of its stock broking arm, nabtrade, now comes from SMSFs. A year ago this share was 19 per cent."NAB considers SMSFs to be a critical customer group," according to internal notes prepared for middle management.UBank, an alternative NAB brand, has "captured a significant share of [the SMSF] market," the notes say.