Discussion and Analysis of Results of Operations
Net Income
Net income for the three months ended September 30, 2022 was $9.6 million, or $0.47 per diluted common share, a $3.4 million, or 26.4%, decrease as compared to $13.1 million, or $0.74 per diluted common share, for the three months ended September 30, 2021. Net income decreased primarily due to a $9.0 million decrease in noninterest income and a $726 thousand increase in noninterest expense, partially offset by a $7.2 million increase in net interest.
Net income for the nine months ended September 30, 2022 was $29.1 million, or $1.56 per diluted common share, a $10.9 million, or 27.2%, decrease as compared to $40.0 million, or $2.26 per diluted common share, for the nine months ended September 30, 2021. The decrease in net income was primarily driven by a $28.0 million decrease in noninterest income, partially offset by an $8.5 million increase in net interest income and a $6.8 million decrease in noninterest expense.
Net Interest Income
Net interest income is the difference between interest income and yield-related fees earned on assets and interest expense paid on liabilities. Net interest margin is the difference between the yield on interest earning assets and the cost of interest-bearing liabilities as a percentage of interest earning assets. Net interest margin is presented on a tax-equivalent basis, which means that tax-free interest income has been adjusted to a pre-tax-equivalent income, assuming a federal income tax rate of 21% for the three and nine months ended September 30, 2022 and 2021.
Net interest income for the three months ended September 30, 2022 was $28.3 million, a $7.2 million, or 34.0%, increase from $21.1 million for the three months ended September 30, 2021. Net interest income increased primarily due to a $9.8 million increase in interest income, due to a $6.5 million increase in interest income received from loans, the result of a $270.4 million increase in loans from the acquisition of Metro Phoenix Bank. Partially offsetting the increase of interest income was a $2.5 million increase in interest expense, primarily due to a $1.5 million increase in interest paid on short-term borrowings. Short-term borrowings increased primarily as a result of seasonally lower deposit balances.
Net interest income for the nine months ended September 30, 2022 was $72.8 million, an increase of $8.5 million, or 13.1%, as compared to the $64.3 million for the nine months ended September 30, 2021. Net interest income increased primarily due to an $8.8 million increase on interest income received from investment securities, partially offset by a $2.9 million increase in interest expense, driven by a $1.8 million increase in interest expense paid on short-term borrowings. Interest income received from investment securities increased, primarily due to an increase in the balance of investment securities available-for-sale. Interest expense paid on short-term borrowings increased primarily as a result of lower deposit balances.
Our net interest margin (on a fully tax-equivalent, or FTE, basis) for the three months ended September 30, 2022 was 3.21%, compared to 2.78% for the same period in 2021. Excluding the acquisition of Metro Phoenix Bank, net interest margin was 3.04% for the third quarter of 2022. Net interest margin increased primarily due to a 69 basis point increase in the yield on interest earning assets, partially offset by a 38 basis point increase in the yield on interest-bearing liabilities. The rate earned on interest earning assets increased primarily due to increases of 186 basis points on the rate earned on interest-bearing deposits with banks, and 102 basis points on the rate earned on Federal Reserve/FHLB stock. The increase in the rate paid on interest-bearing liabilities was primarily due to an increase of 371 basis points in fed funds purchased, the result of a rising interest rate environment as well as seasonally lower deposit balances. Additionally, we saw increases of $441.5 million in average total loans and $275.0 million in average total deposits. Excluding the acquisition of Metro Phoenix Bank, average total loans increased $160.3 million and average total deposits decreased $52.0 million.
Our net interest margin (on a FTE basis) for the nine months ended September 30, 2022 was 3.02%, compared to 2.92% for the same period in 2021. Excluding the acquisition of Metro Phoenix Bank, net interest margin for the nine months ended September 30, 2022 was 2.95%. The increase in net interest margin was primarily due to a 19 basis point