lower funding costs that outpaced the lower overall market interest rates on loans compared to the year ended December 31, 2020.
Interest Income. Interest income increased $29.1 million, or 10%, to $311.9 million for the year ended December 31, 2021, from $282.8 million for the year ended December 31, 2020. This increase was primarily attributable to a $29.9 million increase in interest on loans and a $1.6 million increase in interest on mortgage loans in process of securitization, which was partially offset by a $2.5 million decrease of other interest-bearing assets.
Interest income for loans and loans held for sale increased $29.9 million compared to the year ended December 31, 2020. The average balance of loans, including loans held for sale, during the year ended December 31, 2021 increased $1.5 billion, or 21%, to $8.5 billion from $7.0 billion for the year ended December 31, 2020, reflecting significant increases in loan volume. The average yield on loans decreased 32 basis points, to 3.45%, for the year ended December 31, 2021, compared to 3.77% for the year ended December 31, 2020, due to lower overall interest rates in the economy period to period.
Interest income for mortgage loans in process of securitization increased by $1.6 million compared to the year ended December 31, 2020. The average balance of mortgage loans in process of securitization increased $112.9 million, or 30%, to $494.3 million for the year ended December 31, 2021 from $381.3 million for the year ended December 31, 2020, and the average yield decreased 34 basis points, to 2.58%, for the year ended December 31, 2021, compared to 2.92% for the year ended December 31, 2020.
Interest income for interest-bearing deposits and other assets decreased by $2.5 million compared to the year ended December 31, 2020. The average balance of interest-earning deposits and other assets increased $4.1 million, or 1%, to $669.4 million for the year ended December 31, 2021 from $665.3 million for the year ended December 31, 2020, and the average yield decreased 38 basis points, to 0.29%, for the year ended December 31, 2021, compared to 0.67% for the year ended December 31, 2020.
Interest Expense. Total interest expense decreased $24.8 million, or 42%, to $33.9 million for the year ended December 31, 2021, compared to $58.6 million for the year ended December 31, 2020.
Interest expense on total deposits decreased $24.0 million, or 46%, to $28.3 million for the year ended December 31, 2021 compared to the year ended December 31, 2020. The decrease was attributable to lower volume and rates of certificates of deposits and lower rates of interest-bearing checking.
Interest expenses for certificates of deposit decreased $19.0 million compared to the year ended December 31, 2020. The average balance of certificates of deposits of $687.0 million for the year ended December 31, 2021 decreased $1.0 billion, or 60%, compared to the year ended December 31, 2020. The average yield of certificates of deposits was 0.66% for the year ended December 31, 2021, which was a 70 basis point decrease compared to 1.36% for the year ended December 31, 2020.
Interest expense for interest-bearing checking deposits decreased $5.6 million compared to the year ended December 31, 2020. The decrease was attributable to 23 basis point decrease in the average cost of interest-bearing checking deposits, to 0.14% for the year ended December 31, 2021 from 0.37% for the same period in 2020. Offsetting the lower average cost was a $1.4 billion, or 42%, increase in the average balance of interest-bearing checking deposits, which reached $4.6 billion for the year ended December 31, 2021.
Interest expense on borrowings decreased $770,000, or 12%, to $5.6 million for the year ended December 31, 2021 from $6.4 million for the year ended December 31, 2020. The decrease was due primarily to a 12 basis point decrease in the average cost of borrowings to 0.86%, compared to 0.98% for the year ended December 31, 2020. The average balances for the year ended December 31, 2021 reflected an increase in average borrowing from the FHLB and the American Financial Exchange (“AFX”) at much lower rates. Also included in borrowings, our warehouse structured financing agreement provides for an additional interest payment for a portion of the earnings generated. As a result, the cost of borrowings increased from a base rate of 0.40% and 0.46%, to an effective rate of 0.86% and 0.98% for the year ended December 31, 2021 and 2020, respectively.