tax-equivalent basis), a non-GAAP financial measure which excludes the impact of loan fees, was 2.17% for the nine months ended September 30, 2024, a 22 basis point decline from 2.39% for the nine months ended September 30, 2023.
Average interest earning assets were $4.54 billion for the nine months ended September 30, 2024, an increase of $166.2 million, or 3.8%, compared to $4.38 billion for the nine months ended September 30, 2023. This increase in average interest earning assets was primarily due to organic growth in the loan portfolio, continued purchases of investment securities, and an increase in cash balances. Average interest bearing liabilities were $3.44 billion for the nine months ended September 30, 2024, an increase of $225.8 million, or 7.0%, compared to $3.22 billion for the nine months ended September 30, 2023. The increase in average interest bearing liabilities was primarily due to an increase in interest bearing transaction deposits, time deposits, brokered deposits, and FHLB advances, offset partially by a decrease in federal funds purchased.
Average interest earning assets produced a tax-equivalent yield of 5.39% for the nine months ended September 30, 2024, compared to 5.04% for the nine months ended September 30, 2023. The average rate paid on interest bearing liabilities was 4.16% for the nine months ended September 30, 2024, compared to 3.49% for the nine months ended September 30, 2023.
Interest Income. Total interest income on a tax-equivalent basis was $183.5 million for the nine months ended September 30, 2024, compared to $165.0 million for the nine months ended September 30, 2023. The $18.5 million increase in total interest income on a tax-equivalent basis was primarily due to an increase in cash balances, organic growth in the loan portfolio, purchases of investment securities and higher earning asset yields in the higher interest rate environment.
Interest income on the investment securities portfolio, on a tax-equivalent basis, increased $5.9 million during the nine months ended September 30, 2024, compared to the nine months ended September 30, 2023, primarily due to a $83.1 million, or 13.9%, increase in average balances and a 63 basis point increase in yield between the periods.
Interest income on loans, on a tax-equivalent basis, was $153.6 million for the nine months ended September 30, 2024, compared to $142.7 million for the nine months ended September 30, 2023. The $10.9 million increase was primarily due to a 1.4% increase in the average balances of loans outstanding and a 31 basis point increase in yield.
Interest Expense. Interest expense on interest bearing liabilities was $107.3 million for the nine months ended September 30, 2024, an increase of $23.4 million, compared to $83.9 million for the nine months ended September 30, 2023. The increase was primarily due to growth and continued deposit repricing in the higher interest rate environment, offset partially by decreased utilization of federal funds purchased.
Interest expense on deposits increased to $96.0 million for the nine months ended September 30, 2024, compared to $66.6 million for the nine months ended September 30, 2023. The $29.4 million increase in interest expense on deposits was primarily due to upward repricing of the deposit portfolio in the higher interest rate environment.
Interest expense on borrowings was $11.4 million for the nine months ended September 30, 2024, compared to $17.3 million for the nine months ended September 30, 2023. This decrease was primarily due to lower average balances of federal funds purchased.
Provision for Credit Losses
The provision for credit losses on loans was $-0- for both the third quarter of 2024 and the third quarter of 2023. The provision for credit losses on loans was $1.5 million for the nine months ended September 30, 2024, compared to $2.1 million for the nine months ended September 30, 2023. Although loans decreased during the quarter, increased loss rates and other qualitative factor adjustments resulted in no provision for the quarter. The allowance for credit losses on loans to total loans was 1.38% at September 30, 2024, compared to 1.36% at December 31, 2023.