The average balance of loans during the three months ended September 30, 2022, increased by $4.5 million, or 5.8%, from the average balance for the three months ended September 30, 2021, while the average yield on loans decreased by 16 basis points to 3.34% for the three months ended September 30, 2022, from 3.50% for the three months ended September 30, 2021.
The decrease in average yield on loans was due to the declining interest rates in the early part of the year-to-year period, while the recent increases in rates in the economy have not yet had a significant impact on the overall loan portfolio.
The average balance of investment securities increased $4.9 million, or 17.1%, to $33.7 million for the three months ended September 30, 2022, from $28.8 million for the three months ended September 30, 2021, while the average yield on investment securities increased by 122 basis points to 2.30% for the three months ended September 30, 2022, from 1.08% for the three months ended September 30, 2021. This increase in yields resulted from the effects of management’s sale of lower yielding investments in December 2021 and purchases of higher yielding securities during the quarter ended September 30, 2022.
The average balance of other interest-bearing deposits, comprised of certificates of deposit in other financial institutions, overnight deposits and stock in the Federal Home Loan Bank, increased $14.1 million, or 88.9%, for the three months ended September 30, 2022, and the average yield increased 113 basis points to 1.86% for the three months ended September 30, 2022, from 0.73% for the three months ended September 30, 2021 reflecting the rise in the interest rate environment.
Interest Expense. Total interest expense decreased $23,000, or 24.7%, to $71,000 for the three months ended September 30, 2022, compared to the three months ended September 30, 2021. The decrease was primarily due to a decrease in the average cost of deposits to 0.27% for the three months ended September 30, 2022, from 0.38% for the three months ended September 30, 2021, reflecting how management has worked to manage the cost of deposits over the period as interest rates in the economy have been increasing in recent months, which was partially offset by an increase of $5.1 million, or 5.1%, in the average balance of deposits, to $104.3 million for the three months ended September 30, 2022, compared to the three months ended September 30, 2021.
Net Interest Income. Net interest income increased $257,000, or 37.1%, to $950,000 for the three months ended September 30, 2022, compared to $693,000 for the three months ended September 30, 2021. The increase reflected an increase in the interest rate spread to 2.53% for the three months ended September 30, 2022, from 2.20% for the three months ended September 30, 2021. The net interest margin increased to 2.60% for the three months ended September 30, 2022, from 2.26% for the three months ended September 30, 2021.
Provision for Loan Losses. Based on an analysis of the factors described in “Critical Accounting Policies and Use of Critical Accounting Estimates – Allowance for Loan Losses,” management concluded that a provision for loan losses was not required for each of the three months ended September 30, 2022 and 2021. The allowance for loan losses was $223,000 at both September 30, 2022 and 2021 and represented 0.28% of total loans at September 30, 2022, and 0.29% of total loans at September 30, 2021. The determination over the adequacy of the allowance for loan losses was due primarily to the low balances of nonperforming loans, delinquent loans and no net charge-offs in both periods.
Total nonperforming loans were $278,000 at September 30, 2022, compared to $166,000 at September 30, 2021. Total loans past due greater than 30 days were $175,000 and $455,000 at those respective dates. As a percentage of nonperforming loans, the allowance for loan losses was 80.1% at September 30, 2022, compared to 134.5% at September 30, 2021.
The allowance for loan losses reflects the estimate management believes to be appropriate to cover incurred probable losses which were inherent in the loan portfolio at September 30, 2022 and 2021. While management believes the estimates and assumptions used in the determination of the adequacy of the allowance are reasonable, such estimates and assumptions could be proven incorrect in the future, and the actual amount of future provisions may exceed the amount of past provisions. Furthermore, as an integral part of its examination process, the OCC will periodically review our allowance for loan losses. The OCC may have judgments different than those of management, and we may determine to increase our allowance as a result of these regulatory reviews. Any material increase in the allowance for loan losses may adversely affect our financial condition and results of operations.
Non-Interest Income. Non-interest income was consistent between the three months ended September 30, 2022 and 2021, totaling $54,000 for the three months ended September 30, 2022, a zero net change, from $54,000 for the three months ended September 30, 2021.