Insured deposits accounted for approximately 85% of total deposits as of March 31, 2023.
Our loan to deposit ratio measured 106.1% as of March 31, 2023, compared to 103.5% as of December 31, 2022. The loan to deposit ratio measured 100.3% for the first quarter 2023 when calculated based on the average balances of loans and deposits for the quarter opposed to measuring such balances as of the last day of the quarter. This is more reflective of the actual management of the portfolios during the entire quarter, particularly in the wake of the banking industry events that followed the announced closure of Silicon Valley Bank and Signature Bank in mid-March, 2023.
Borrowings were $2.3 billion as of March 31, 2023, compared to $1.4 billion as of December 31, 2022. The increase in borrowings compared to the prior quarter was primarily due to the addition of $1.2 billion in FHLB advances offset by $200 million paydown of fed funds balances outstanding. Average borrowings outstanding for the quarter ended March 31, 2023 were $1.4 billion compared to $1.5 billion for the quarter ended December 31, 2022. The additional borrowings for the quarter-ended March 31, 2023 were utilized to increase on-balance sheet liquidity, notably in the wake of banking industry events that followed the announced closure of Silicon Valley Bank and Signature Bank in mid-March 2023.
Private Wealth Management and Trust Assets
AUM was $5.2 billion as of March 31, 2023, compared to $5.0 billion as of December 31, 2022. The net change in AUM balance of $0.2 billion is comprised of the following: $86 million of new accounts; $120 million of net withdrawals; and $277 million of performance gains. AUA at FFB’s Trust Department was unchanged at $1.3 billion as of March 31, 2023, compared to December 31, 2022.
Net Interest Income and Net Interest Margin (“NIM”)
Net interest income was $58.8 million for the first quarter of 2023, compared to $74.7 million and $74.5 million for the fourth and first quarters of 2022, respectively. Interest income increased to $137 million for the first quarter of 2023 compared to $126.0 million and $79.1 million for the fourth and first quarters of 2022, respectively. The increase in interest income was due to increases in both average interest-earning asset balances as well as average yields earned on such balances. Average interest-earning asset balances increased to $12.7 billion for the quarter ended March 31, 2023, compared to $12.2 billion and $9.9 billion for the quarters ended December 31, and March 31, 2022, respectively. Yields on interest-earning assets averaged 4.32% for the first quarter of 2023, compared to 4.12% and 3.19% for the fourth and first quarters of 2022, respectively.
Interest expense was $78.2 million for the first quarter of 2023, compared to $51.3 million and $4.7 million for the fourth and first quarters of 2022, respectively. The increase in interest expense was due to increases in both average interest-bearing liability balances as well as average rates paid on such balances. Average interest-bearing liability balances, consisting of interest-bearing deposits and borrowings, increased to $9.3 billion for the quarter ended March 31, 2023, compared to $8.1 billion and $5.9 billion for the quarters ended December 31, and March 31, 2022, respectively. Rates on interest-bearing liability balances averaged 3.41% for the first quarter of 2023, compared to 2.52% and 0.32% for the fourth and first quarters of 2022, respectively.
The 0.20% increase in average yield earned on interest-earning assets was offset by an 0.89% increase in average rate paid on interest-bearing liability balances, resulting in a contraction of net interest margin (“NIM”) for the quarter ended March 31, 2023. NIM was 1.83% for the first quarter of 2023 compared to 2.45% and 3.0% for the fourth and first quarters of 2022, respectively.