Comparison of Operating Results for the Three Months Ended September 30, 2022 and 2021
General. Net income decreased by $271,000, or 6.5%, to $3.9 million for the three months ended September 30, 2022 from $4.2 million for the three months ended September 30, 2021. The decrease in net income was primarily due to a $608,000 decrease in non-interest income, a $205,000 increase in non-interest expense and a $58,000 reduction in the reversal of loan loss provisions. These decreases to net income were partially offset by a $478,000 increase in net interest income and a $122,000 decrease in income tax expense.
Net Interest Income. Net interest income increased by $478,000, or 3.4%, to $14.3 million for the three months ended September 30, 2022 from $13.9 million for the three months ended September 30, 2021. Interest income increased by $876,000, or 5.7%, primarily due to a 10 basis point increase in the yield on average interest-earning assets and a $47.1 million increase in the average balance of interest-earning assets. Interest expense increased by $398,000, or 28.2%, due to an eight basis point increase in the cost of average interest-bearing liabilities and a $53.7 million increase in the average balance of interest-bearing liabilities. The net interest rate spread and net interest margin were 2.69% and 2.75%, respectively, for the three months ended September 30, 2022, compared to 2.67% and 2.72%, respectively, for the three months ended September 30, 2021. The increase in the net interest rate spread and in the net interest margin are attributable to the 10 basis point increase in the yield of average interest-earning assets, which was partially offset by the eight basis point increase in the cost of average interest-bearing liabilities.
Interest Income. Interest income increased by $876,000, or 5.7%, to $16.2 million for the three months ended September 30, 2022 from $15.3 million for the three months ended September 30, 2021. Interest income on securities increased by $1.2 million, or 35.4%, to $4.4 million for the three months ended September 30, 2022 from $3.3 million for the three months ended September 30, 2021. The increase in interest income on securities occurred primarily because the average balance of securities increased by $127.2 million, or 20.8%, to $739.6 million for the three months ended September 30, 2022 from $612.4 million for the three months ended September 30, 2021. The increase in the average balance of securities occurred as mortgage-backed securities were purchased to offset the decrease in interest income on our loan portfolio. The increase in interest income on investment securities was augmented by a 26 basis point increase in the average yield. The increase to interest income on investment securities was partially offset by a decrease in interest income on loans of $460,000, or 3.9%, from $11.8 million for the three months ended September 30, 2021 to $11.4 million for the three months ended September 30, 2022. The decrease in interest income on loans occurred because of an eight basis point decrease in the average yield and a $19.9 million, or 1.5%, decrease in the average balance of loans. The decrease in the average yield occurred as higher yielding loans were paid off and new loans with lower interest rates were added to the loan portfolio. The decrease in the average yield occurred as loans with lower interest rates had been added to the loan portfolio and higher yielding loans continue to be paid down. Despite an increase in current market rates, the average yield decreased in the three months ended September 30, 2022, due to a low amount of new loan originations at these higher market rates.
Interest Expense. Interest expense increased by $398,000, or 28.2%, to $1.8 million for the three months ended September 30, 2022 from $1.4 million for the three months ended September 30, 2021. Interest expense on interest-bearing deposits increased by $398,000, or 47.2%, to $1.2 million for the three months ended September 30, 2022 from $844,000 for the three months ended September 30, 2021. The increase in interest expense on interest-bearing deposits was primarily due to a $78.0 million, or 31.6% increase in the average balance of certificates of deposit and a 28 basis point increase in the average rate on certificates of deposit. The increase in the average balance of certificates of deposit included a $38.4 million increase in the average balance of public deposits and also occurred as customers transferred funds from savings accounts to certificates of deposit with higher interest rates. The average rate paid on average certificates of deposit increased to 1.24% for the three months ended September 30, 2022 from 0.96% for the three months ended September 30, 2021, primarily due to increases in market rates.
Provision for Loan Losses. We recorded a reversal of loan loss provisions of $109,000 and $167,000 for the three months ended September 30, 2022 and 2021, respectively. The reversal of loan loss provisions occurred primarily due to decreases in the amount of loans in our loan payment deferral program, Hawaii’s unemployment rate and the size of our loan portfolio. The loan payment deferral program was created to assist borrowers who were experiencing financial hardship due to the COVID-19 pandemic. The provisions recorded resulted in ratios of the allowance for loan losses to total loans of 0.16% and 0.21% at September 30, 2022 and 2021, respectively. Nonaccrual loans totaled $2.0