LIFE assurer Old Mutual said on Thursday that its subsidiary bank, Nedcor Ltd, has earned better-than-expected interest income and margins, but these have been partially offset by bad debt. Old Mutual, which owns a 53,5% controlling interest in the bank, said Nedcor continues to place a considerable focus on expense control in seeking to achieve its objective of a cost-to-income ratio of 50% within the next three years.