The average balance of loans during the year ended September 30, 2023 increased by $5.2 million, or 4.6%, from the balance for the year ended September 30, 2022, while the average yield on loans increased by 72 basis points to 4.49% for the year ended September 30, 2023 from 3.77% for the year ended September 30, 2022. The increase in average yield on loans reflects the increase in the overall interest rate environment year to year. As interest rates began to increase during the Bank’s fiscal 2022 year, the interest rates on the Bank’s adjustable-rate loans have adjusted upward and should continue to rise provided the higher interest rate environment persists.
The average balance of investment securities increased $2.1 million to $13.8 million for the year ended September 30, 2023 from $11.7 million for the year ended September 30, 2022, while the average yield on investment securities increased by 89 basis points to 1.91% for the year ended September 30, 2023 from 1.02% for the year ended September 30, 2022.
Interest income on other interest-bearing deposits, comprised primarily of certificates of deposit in other financial institutions, overnight deposits and stock in the Federal Home Loan Bank, increased $210,000, or 57.9%, for the year ended September 30, 2023, due to an increase in the average yield of 344 basis points, to 4.19% for the year ended September 30, 2023 from 0.75% for the year ended September 30, 2022, partially offset by a decrease in the average balance of $11.6 million. The increase in average yield was due to the increase in interest rates in the overall economy during the periods.
Interest Expense. Total interest expense increased $335,000, or 55.8%, to $600,000 for the year ended September 30, 2023 from $265,000 for the year ended September 30, 2022. Interest expense on deposits increased $253,000, or 52.0%, due primarily to an increase of 23 basis points in the average cost of deposits to 0.43% for the year ended September 30, 2023 from 0.20% for the year ended September 30, 2022, which was partially offset by a decrease of $5.7 million, or 4.8%, in the average balance of interest-bearing deposits to $112.5 million for the year ended September 30, 2023 from $118.2 million for the year ended September 30, 2022.
Interest expense on borrowings increased $82,000, or 71.8%, for the year ended September 30, 2023, compared to the year ended September 30, 2022. The increase was due to a 166 basis point increase in the weighted-average rate, to 2.58% for the year ended September 30, 2023 and a $1.0 million increase in the average balance outstanding, to $4.5 million for the year ended September 30, 2023 from $3.5 million for the year ended September 30, 2022.
Net Interest Income. Net interest income increased $1.1 million, or 19.9%, to $5.4 million for the year ended September 30, 2023 compared to $4.3 million for the year ended September 30, 2022. The increase reflected an increase in the interest rate spread to 3.71% for the year ended September 30, 2023 from 2.92% for the year ended September 30, 2022, while the average net interest earning assets increased $365,000 year to year. Our net interest margin increased to 3.80% for the year ended September 30, 2023 from 2.95% for the year ended September 30, 2022. The interest rate spread and net interest margin were impacted by a series of interest rate increases in the economy during 2023 and 2022.
Provision for Loan Losses. Based on an analysis of the factors described in “Critical Accounting Policies—Allowance for Loan Losses,” management determined that a provision for loan losses was not required for the year ended September 30, 2023, resulting in a decrease of $25,000 from the provision recorded for the year ended September 30, 2022. The allowance for loan losses was $934,000 at September 30, 2023 and $984,000 at September 30, 2022 and represented 0.70% of total loans at September 30, 2023, and 0.81% of total loans at September 30, 2022. The determination of the adequacy of the allowance for loan losses was due primarily to the low balances of nonperforming loans and delinquent loans.
Total nonperforming loans were $477,000 at September 30, 2023, compared to $350,000 at September 30, 2022. Classified loans totaled $477,000 at September 30, 2023, compared to $350,000 at September 30, 2022, and total loans past due greater than 30 days were $1.3 million and $830,000 at those respective dates. As a percentage of nonperforming loans, the allowance for loan losses was 195.7% at September 30, 2023 compared to 281.2% at September 30, 2022.