For the nine months ended September 30, 2024, the average balance of interest-earning assets decreased by $47.6 million, or 3.8%, to $1.20 billion while the average yield improved by 45 basis points to 5.28%, when compared to the nine months ended September 30, 2023. The average balance of interest-bearing liabilities decreased by $27.7 million, or 3.0%, primarily due to a decrease in deposits, partially offset by the increase in the average balance of FHLB advances, while the cost of interest-bearing liabilities increased by 59 basis points to 2.92%. The net interest margin decreased by 1 basis point to 3.08% and the interest rate spread decreased by 13 basis points to 2.36% for the nine months ended September 30, 2024 from the same period in 2023.
The provision for credit losses decreased by $21,000, or 2.3%, from $910,000 for the quarter ended September 30, 2023 to $889,000 for the quarter ended September 30, 2024. The provision for credit losses decreased by $53,000, or 3.6%, from $1.47 million for the nine months ended September 30, 2023 to $1.42 million for the nine months ended September 30, 2024. These decreases to the provision for the three months and the nine months ended September 30, 2024 were primarily attributable to a decrease in loan balances, primarily indirect automobile loans.
Net charge-offs decreased $41,000 from $385,000 for the third quarter of 2023 to $344,000 for the third quarter of 2024. The decrease was primarily due to decreased net charge-offs in indirect automobile loans of $216,000 and recoveries in residential real estate and commercial loans in the third quarter of 2023. Net charge-offs increased $8,000, or 0.6%, to $1.4 million for the first nine months of 2024. The percentage of overdue account balances to total loans decreased to 1.62% as of September 30, 2024, from 1.90% as of December 31, 2023, while non-performing assets increased $584,000, or 13.9%, to $4.8 million at September 30, 2024.
Non-interest (loss) income totaled $(10.0) million for the three months ended September 30, 2024, a decrease of $11.7 million, from $1.6 million for the comparable period in 2023, due primarily to the $12.0 million loss on sale of investment securities resulting from the previously mentioned balance sheet restructuring. Excluding the securities loss, non-interest income for the third fiscal quarter of 2024 would have been $2.0 million compared to $1.6 million for the three months ended September 30, 2023. The Company also recorded an increase of $54,000, or 16.8%, in investment advisory income resulting from the improved market and economic conditions, an increase of $35,000 in service charges on deposit accounts, an increase of $22,000 in the cash surrender value of life insurance, and an increase in the gain on sales of loans of $20,000.
Non-interest (loss) income totaled $(7.0) million for the nine months ended September 30, 2024, a decrease of $11.4 million, from $4.4 million for the comparable period in 2023, due primarily to the $12.0 million loss on sale of investment securities resulting from the previously mentioned balance sheet restructuring. Excluding the securities loss, non-interest income for the nine months ended September 30, 2024 would have been $5.0 million compared to $4.4 million for the nine months ended September 30, 2023. The Company recorded an increase of $270,000, or 31.3%, in investment advisory income resulting from the improved market and economic conditions, an increase of $194,000 related to gains on life insurance, an increase of $88,000 in service charges on deposit accounts, an increase of $70,000, or 14.2%, in the cash surrender value of life insurance, and an increase in the gain on sales of loans of $39,000, partially offset by a decrease of $54,000 on the disposal of premises and equipment.
Non-interest expense totaled $9.1 million for the third quarter of 2024, an increase of $266,000, or 3.0%, over the comparable period in 2023. The increase was primarily due to a $370,000 increase in salaries and benefits related primarily due to higher production commissions and higher medical insurance costs. This increase was partially offset by a $109,000 decrease in other non-interest expense primarily due to a decrease in lending operations expense.