Net interest margin was 9.44%, up 16 basis points from the prior year. The increase in net interest margin from the prior year reflects decreased funding costs partially offset by lower loan yield. Credit card yield was 11.97%, a decrease of 24 basis points from the prior year. The decline in credit card yield from the prior year reflects an increase in promotional rate balances and a decline in higher rate balances, partially offset by lower interest charge-offs. Interest expense as a percent of total loans decreased 39 basis points from the prior year as the company continued to take advantage of available low rate funding.
Net interest income increased $116 million, or 9%, from the prior year, benefiting from loan growth and lower interest expense, which was partially offset by a decline in loan yield.
Other income increased $66 million, or 14%, from the prior year primarily due to revenue from Discover Home Loans and higher net interchange revenue as a result of increased sales.
The delinquency rate for credit card loans over 30 days past due was 1.58%, an improvement of 27 basis points from the prior year, and a decrease of 19 basis points from the prior quarter. Credit card net charge-off rate for the second quarter was 2.34%, down 38 basis points from the prior year, and down 2 basis points from the prior quarter. The student loan net charge-off rate excluding PCI loans was 1.58%, up 85 basis points from the prior year and 76 basis points sequentially, due to a larger portion of the portfolio entering repayment and seasonality, respectively. Personal loan net charge-off rate decreased 1 basis point from the prior year and 6 basis points sequentially to 2.24%.Provision for loan losses of $225 million decreased $37 million from the prior year, driven by a decline in charge-offs and a higher reserve release. The reserve release for the second quarter of 2013 was $93 million reflecting the impact of a 21 basis point decline in the reserve rate from the prior quarter partially offset by additional reserves due to loan growth. The second quarter of 2012 included a reserve release of $73 million. Net principal charge-offs were $17 million lower than the prior year as a result of the continued decline in delinquencies and bankruptcies.