Discover card sales volume grew 4% from the prior year to $27.2 billion. Credit card loans ended the quarter at $48.1 billion, up 4%, or $1.9 billion, from the prior year.
Total loans ended the quarter at $59.2 billion, up $5.1 billion, or 9%, compared to the prior year. Private student loans increased $2.9 billion, including the acquisition of a $2.4 billion student loan portfolio in the fourth quarter of 2011. Personal loans increased $675 million from the prior year.
Net interest margin was 9.44%, up 18 basis points from the prior year. The increase in net interest margin from the prior year reflects decreased funding costs partially offset by lower total yield. Credit card yield was 12.27%, a decrease of 19 basis points from the prior year. The decline in credit card yield from the prior year reflects a decline in higher rate balances and an increase in promotional rate balances, partially offset by lower interest charge-offs. Interest expense as a percent of total loans decreased 47 basis points from the prior year as the company continued to take advantage of available low rate funding.
Net interest income increased $133 million, or 11%, from the prior year, benefiting from loan growth and lower interest expense. This was partially offset by a decline in credit card and student loan yields. The delinquency rate for credit card loans over 30 days past due was 1.81%, an improvement of 62 basis points from the prior year. The credit card net charge-off rate decreased to 2.43% for the third quarter of 2012, down 142 basis points from the prior year.
Net charge-offs were $151 million lower than the prior year as a result of the continued decline in delinquencies and bankruptcies. Provision for loan losses of $126 million increased $26 million, or 26%, from the prior year, driven by a lower reserve release partially offset by the decline in charge-offs. The reserve release for the third quarter of 2012 was $182 million reflecting the impact of a 43 basis point decline in the reserve rate from the prior quarter partially offset by additional reserves due to loan growth. The third quarter of 2011 included a reserve release of $359 million.