Net interest and dividend income was $55.6 million in the third quarter of 2022, compared to $22.6 million in the third quarter of 2021. The $33.0 million increase was primarily driven by growth in most interest and dividend income categories due to West Suburban related loan and securities income being reflected. In addition we experienced an increase in interest expense in the third quarter of 2022, compared to the third quarter of 2021, primarily due to a rise in deposit interest rates and increased balances from West Suburban, an increase in other short-term borrowings due to an FHLB advance, and an increase in the rate paid on our senior notes during the third quarter of 2022, as the interest rate payable on these notes became floating as of January 1, 2022, at three month LIBOR plus 385 basis points, compared to the prior 5.75% fixed rate.
Average loans, including loans held for sale, increased $1.86 billion in the third quarter of 2022, compared to the third quarter of 2021, primarily from $1.50 billion of average loans acquired in our acquisition of West Suburban. Also contributing to the increase was $244.3 million in average loan growth during the third quarter of 2022, less PPP loans forgiven or repaid and loan paydowns.
Nine months ended September 30, 2022 and 2021
Our income before taxes was $59.7 million for the nine months ended September 30, 2022 compared to $39.4 million for the nine months ended September 30, 2021. This increase in pretax income was primarily due to a $74.0 million increase in interest and dividend income, and a $5.6 million increase in noninterest income, as West Suburban loan, security and fee income are included in the nine months ended September 30, 2022. These increases were partially offset by a $46.2 million increase in noninterest expense, primarily due to an increase in salaries and employee benefits, occupancy, furniture and equipment expense, computer and data processing expense, other expense, and amortization of core deposit intangible. The majority of these increases were due to the inclusion of operating costs of the legacy West Suburban staff and branches, as well as $9.5 million of West Suburban acquisition-related costs in the first nine months of 2022, primarily within computer and data processing. Our net income was $43.8 million, or $0.97 per diluted share, for the nine months ended September 30, 2022, compared to net income of $29.1 million, or $0.99 per diluted share, for the same period of 2021.
Net interest and dividend income was $142.1 million for the nine months ended September 30, 2022, compared to $68.1 million for the same period of 2021. The $74.0 million increase was primarily driven by growth in most interest and dividend income categories due to West Suburban related loan and securities income being reflected. This increase was partially offset by a $402,000 increase in interest expense for the nine months ended September 30, 2022, compared to the same period of 2021, primarily due to three full periods of interest expense on the April 2021 issuance of subordinated debt in 2022, as well as higher average balances of deposits from the West Suburban acquisition, partially offset by a decrease in outstanding balances of notes payable and a decrease in the rate paid on our senior notes during 2022, as the interest rate payable on these notes became floating as of January 1, 2022, at three month LIBOR plus 385 basis points, compared to the prior 5.75% fixed rate.
Net Interest Income
Net interest income, which is our primary source of earnings, is the difference between interest income earned on interest-earning assets, such as loans and investment securities, as well as accretion income on purchased loans, and interest incurred on interest-bearing liabilities, such as deposits and borrowings. Net interest income depends upon the relative mix of interest-earning assets and interest-bearing liabilities, the ratio of interest-earning assets to total assets and of interest-bearing liabilities to total funding sources, and movements in market interest rates. Our net interest income can be significantly influenced by a variety of factors, including overall loan demand, economic conditions, credit risk, the amount of nonearning assets including nonperforming loans and OREO, the amounts of and rates at which assets and liabilities reprice, variances in prepayment of loans and securities, early withdrawal of deposits, exercise of call options on borrowings or securities, a general rise or decline in interest rates, changes in the slope of the yield-curve, and balance sheet growth or contraction.
Three months ended September 30, 2022 and 2021
Our net interest and dividend income increased by $33.0 million to $55.6 million, for the third quarter of 2022, from $22.6 million for the third quarter of 2021. This increase was primarily attributable to a $33.2 million increase in total interest and dividend income due to the acquisition of West Suburban in December 2021. In addition we experienced an increase in interest expense in the third quarter of 2022, compared to the third quarter of 2021, primarily due to increased balances from West Suburban, increased other short-term borrowings expense due to an FHLB advance, and an increase in the rate paid on our senior notes during 2022, as the interest rate payable on these notes became floating as of January 1, 2022, at three month LIBOR plus 385 basis points, compared to the prior 5.75% fixed rate.
Average earning assets for the third quarter of 2022 totaled $5.61 billion, a decrease of $141.5 million, or 2.5%, compared to the second quarter of 2022, and an increase of $2.52 billion, or 81.7%, compared to the third quarter of 2021. Average interest earning deposits with