primarily attributable to a $231,000 decrease in interest income on loans receivable. The decrease in interest income on loans was due to a reduction in the average balance of our loans of $14.4 million, or 9.0%, to $146.4 million for the three months ended March 31, 2021 from $160.8 million for the three months ended March 31, 2020, coupled with a decrease in the average yield on loans of 14 basis points to 4.91% for the three months ended March 31, 2021 from 5.05% for the three months ended March 31, 2020.
Interest Expense. Total interest expense decreased $235,000, or 51.3%, to $223,000 for the three months ended March 31, 2021 from $458,000 for the three months ended March 31, 2020. The decrease was primarily due to a $130,000, or 65.7%, reduction in interest expense on FHLB advances to $68,000 in the three months ended March 31, 2021 compared to $198,000 in the three months ended March 31, 2020. As a result of the prepayment of FHLB advances in the fourth quarter of 2020, the average balance of our FHLB advances was $8.9 million during the three months ended March 31, 2021 compared to $25.0 million during the three months ended March 31, 2020. Interest expense on deposits was $155,000 during the three months ended March 31, 2021, a $105,000, or 40.4%, reduction compared to $260,000 of interest expense on deposits in the three months ended March 31, 2020. While the average balance of our total interest-bearing deposits increased by $16.6 million, or 13.2%, to $142.5 million in the three months ended March 31, 2021 compared to the three months ended March 31, 2020, the average rate paid on interest-bearing deposits decreased by 40 basis points to 0.44% in the first quarter of 2021 compared to the first quarter of 2020.
Net Interest Income. Net interest income was $1.7 million for the three months ended March 31, 2021, a decrease of $36,000, or 2.1%, compared to the three months ended March 31, 2020. Our interest rate spread decreased to 3.04% for the three months ended March 31, 2021 from 3.06% for the three months ended March 31, 2020, and our net interest margin decreased to 3.21% for the three months ended March 31, 2021 from 3.39% for the three months ended March 31, 2020. The decreases in interest rate spread and net interest margin primarily reflect the effects of the continuing low interest rate environment.
Provision for Loan Losses. We recorded no provision for loan losses for the three months ended March 31, 2021, compared to a $65,000 provision for the three months ended March 31, 2020. The decrease in the provision for loan losses for the three months ended March 31, 2021 compared to the three months ended March 31, 2020 resulted from our analysis of the factors described in “Management’s Discussion and Analysis of Financial Condition and Results of Operations — Critical Accounting Policies — Allowance for Loan Losses.” The ratio of non-accrual loans as a percent of total loans outstanding was 0.98% at March 31, 2021 compared to 1.01% at March 31, 2020, and the ratio of our allowance for loan losses to non-performing loans was 174.9% at March 31, 2021 compared to 107.0% at March 31, 2020.
Non-interest Income. Non-interest income increased $33,000, or 17.4%, to $223,000 for the three months ended March 31, 2021 from $190,000 for the three months ended March 31, 2020. The increase was primarily due to a $40,000 increase in other non-interest income, primarily related to an increase in SBA fee income, and a $25,000 gain on the sale of fixed assets, partially offset by a $37,000 decrease in service charges on deposit accounts in the quarter ended March 31, 2021 compared to the quarter ended March 31, 2020.
Non-interest Expense. Non-interest expense increased $86,000, or 5.2%, to $1.7 million for the three months ended March 31, 2021 from $1.6 million for the three months ended March 31, 2020. The increase was due primarily to an $80,000 increase in salaries and employee benefit expense, due in part to new employee hires, a $38,000 increase in occupancy and equipment expense, primarily reflecting expense related to the additional branch office that we opened in 2020, and a $24,000 increase in computer services expense, primarily reflecting systems upgrades. These increases were partially offset by a $31,000 reduction in real estate owned expense and a $26,000 reduction in advertising and marketing expense in the quarter ended March 31, 2021 compared to the quarter ended March 31, 2020.
Upon consummation of the conversion and stock offering, we expect non-interest expense to increase because of costs associated with operating as a public company, including the Louisiana shares tax, and the increased compensation expenses associated with the purchase of shares of common stock by our employee stock ownership plan and the possible implementation of a stock-based benefit plan, if approved by our shareholders. We also will incur increased non-interest expense due to the implementation of our business strategy, including the planned additions to our employee base and our planned new branch opening. In addition, we recently discovered that one of our business customers had been the target of an apparent fraud