Interest income on interest bearing deposits decreased $1.8 million as a result of a $132.6 million decrease in the average balance of interest bearing deposits and a 219 basis point decrease in the average yield on interest bearing deposits to 0.31% for the three months ended June 30, 2020 from 2.50% for the three months ended June 30, 2019.
Interest income on investment securities available-for-sale decreased $187,000 as a result of a 128 basis point decrease in the average yield on investment securities to 2.45% for the three months ended June 30, 2020 from 3.73% for the three months ended June 30, 2019, partially offset by a $21.5 million increase in the average balance of investment securities available-for-sale during the same periods.
Interest income for the six months ended June 30, 2020 was $45.3 million, compared to $34.3 million for the six months ended June 30, 2019, an increase $11.0 million or 32.1%. The increase in interest income was due to an increase in average interest earning assets, principally loans, which was driven primarily by our recent acquisitions and organic growth. Average interest earning assets increased $518.2 million or 35.8% for the six months ended June 30, 2020, compared to the same period in 2019. Interest on loans, including fees, increased $14.0 million, or 49.1%, primarily as a result of a $605.8 million increase in the average loan balance, partially offset by a 40 basis point decrease in the average loan yield during the six months ended June 30, 2020 as compared to this same period in 2019. The average yield on loans for the six months ended June 30, 2020 was 5.23%, compared to 5.63% for the same period in 2019. The average yield on loans for the accretion of the net discount on acquired loans increased the average yield on loans by 33 basis points during the six months ended June 30, 2020 and 2019. During the six months ended June 30, 2020 compared to this same period in 2019, the accretion of the net discount on acquired loans increased the yield on loans by 44 basis points and 33 basis points, respectively. Interest income on loans for the six months ended June 30, 2020 included $3.6 million in accretion of purchase accounting fair value adjustments on acquired loans, compared to $1.7 million for the six months ended June 30, 2019. The remaining net discount on these purchased loans was $4.9 million and $9.3 million at June 30, 2020 and 2019, respectively.
Interest income on interest earning deposits decreased $3.0 million as a result of a $115.5 million decrease in the average balance of interest earning deposits and a 152 basis point decrease in the average yield on interest earning deposits to 0.99% for the six months ended June 30, 2020 from 2.51% for the six months ended June 30, 2019.
Interest income on investment securities decreased $75,000 as a result of a 75 basis point decrease in the average yield on investment securities to 2.50% for the six months ended June 30, 2020 from 3.25% for the six months ended June 30, 2019, partially offset by a $22.9 million increase in the average balance of investment securities available-for-sale.
Interest expense. Interest expense decreased $68,000, or 3.5%, to $1.9 million for the three months ended June 30, 2020 compared to the three months ended June 30, 2019. The average cost of interest bearing liabilities decreased 22 basis points to 0.60% for the three months ended June 30, 2020 from 0.82% for the three months ended June 30, 2019. Total average interest bearing liabilities increased $292.3 million, or 30.9%, to $1.2 billion for the three months ended June 30, 2020 from $947.1 million for the three months ended June 30, 2019. Interest expense on deposits decreased $107,000, or 6.0%, to $1.7 million during the three months ended June 30, 2020 from $1.8 million during this same period in 2019, primarily due to a decrease in the rate paid on interest bearing deposits and despite an increase in the average balance. The average rate paid on interest bearing deposits decreased by 19 basis points to 0.57% for the three months ended June 30, 2020, from 0.76% for the three months ended June 30, 2019, due to lower deposit pricing after the targeted federal funds rate decreases. The overall average cost of deposits for the second quarter of 2020 declined to 0.36%, compared to 0.51% for the second quarter of 2019 due to a reduction in market interest rates over the last year. In addition, the average balance of noninterest bearing deposits increased $201.6 million, or 42.9%, to $671.4 million for the three months ended June 30, 2020 compared to $469.8 million for the same period in 2019. The market’s response to lowering deposit pricing to reflect the targeted federal funds rate decreases over the past year typically lags declines in the yield on interest earning assets.
Interest expense on borrowings increased $39,000, or 26.4%, to $187,000 for the three months ended June 30, 2020, from $148,000 for the three months ended June 30, 2019, as a result of a higher average balance of borrowing outstanding. The average balance of borrowing outstanding increased $51.4 million to $59.6 million during the three months ended June 30, 2020, compared to $8.2 million during the comparable period in 2019. The sharp decline in the average cost of borrowing to 1.26% for the three months ended June 30, 2020, from 7.25% for the three months ended June 30, 2019, offset the significant increase in the average balance of borrowings outstanding.