Interest income on loans decreased $1.5 million, or 4.7%, to $31.0 million for the year ended December 31, 2020 compared to $32.5 million for the year ended December 31, 2019. The decrease was primarily the result of a 26 basis point decrease in the average yield on loans receivable to 4.15% for the year ended December 31, 2020 from 4.41% for the year ended December 31, 2019. The decrease in interest income resulting from the decrease in the average yield was partially offset by an increase in the average balance of loans receivable of $6.8 million , or 0.9%, to $737.9 million for the year ended December 31, 2020 compared to the prior year.
Interest income on investment and mortgage-backed securities decreased by $517,000, or 12.2%, to $3.7 million for the year ended December 31, 2020 from $4.2 million for the year ended December 31, 2019. The decrease was primarily the result of a 40 basis point decrease in the average yield earned on investment and mortgage-backed securities to 2.23% for the year ended December 31, 2020 from 2.63% for the year ended December 31, 2019. The decrease in the average yield was the result of purchases made during the year at a lower rate than those being called and sold due to the declining rate environment. The decrease in interest income resulting from the decrease in the average yield was partially offset by an increase in the average balance of investment and mortgage-backed securities of $5.6 million, or 3.5%, to $166.1 million for the year ended December 31, 2020 compared to the prior year.
Interest income on FHLB stock and other restricted stock decreased $112,000 or 18.1% to $506,000 for the year ended December 31, 2020 compared to $618,000 for the year ended December 31, 2019. The decrease was primarily the result of a 207 basis point decrease in the average yield to 5.98% for the year ended December 31, 2020 from 8.05% for the year ended December 31, 2019. The FHLB decreased the dividend yield on both activity and membership stock as of the first quarter of 2020. The true up that was required for the dividend received was booked in the second quarter of 2020. The decrease in interest income resulting from the decrease in the average yield was partially offset by an increase in the average balance of FHLB stock and other restricted stock of $763,000, or 9.9%, to $8.4 million for the year ended December 31, 2020 compared to the prior year. The overall increase in the average balance of FHLB stock required was due to an increase in the outstanding balance of MPF loans during the year.
Interest income on interest-earning deposits decreased $237,000 or 63.7% to $135,000 for the year ended December 31, 2020 compared to $372,000 for the year ended December 31, 2019. The decrease was primarily the result of a 182 basis point decrease in the average yield on interest-earning deposits to 0.26% due to lower short-term interest rates for much of the year ended December 31, 2020 from 2.08% for the year ended December 31, 2019. The decrease in interest income resulting from the decrease in the average yield was partially offset by an increase in the average balance of interest-earning deposits of $32.9 million, or 184.0%, to $50.9 million for the year ended December 31, 2020 compared to the prior year.
Interest Expense. Total interest expense decreased by $1.9 million, or 20.2%, to $7.4 million for the year ended December 31, 2020 from $9.3 million for the year ended December 31, 2019. The decrease was primarily the result of a 30 basis point decrease in the average cost of interest-bearing liabilities to 1.01% due to lower short-term interest rates for much of the year ended December 31, 2020 from 1.31% for the prior year.
Interest expense on deposits decreased by $1.7 million, or 24.4%, to $5.3 million for the year ended December 31, 2020 from $7.0 million for the year ended December 31, 2019. The decrease was primarily the result of a 32 basis point decrease in the cost of interest-bearing deposits to 0.85% due to lower short-term interest rates for much of the year ended December 31, 2020 from 1.17% for the year ended December 31, 2019. Additionally, the average balance of time deposits decreased $18.5 million, or 7.5%, for the year ended December 31, 2020 compared to the prior year. Partially offsetting those decreases was an increase in the average balance of demand and NOW deposit accounts, savings accounts, and money market accounts of $18.2 million or 17.2%, $12.1 million or 8.5%, and $11.5 million or 10.9%, respectively, for the year ended December 31, 2020 compared to the prior year.
Interest expense on borrowed funds decreased $167,000, or 7.4%, to $2.1 million for the year ended December 31, 2020 from $2.3 million for the year ended December 31, 2019. The decrease was primarily the result of an 11 basis point decrease in the average cost of borrowings to 2.07% for the year ended December 31, 2020 from 2.18% for year ended December 31, 2019. The decrease in the average cost of borrowed funds was primarily the result of new FHLB advances being entered into at rates lower than the average rate on existing borrowings as well as maturities during the period.