Interest and Dividend Income. Interest and dividend income on a tax equivalent basis decreased $1.7 million, or 4.4%, to $36.6 million for the three months ended June 30, 2020, compared to $38.3 million for the three months ended June 30, 2019. All adjustable rate products were negatively impacted by the Federal Reserve cuts to the federal funds rate, and although loan origination volume was strong, lower rates on loan originations also negatively impacted interest and dividend income. For the three months ended June 30, 2020, the primary components of the decrease were a $1.5 million decrease in interest on total loans, a $450,000 decrease investment income and a $209,000 decrease in interest on other interest earning assets, partially offset by a $446,000 increase in interest on loans held for sale. The increase in interest on loans held for sale reflected a higher average balance due to residential real estate mortgage loan demand. The decrease in interest income on loans reflected the 85 basis points decrease in the average yield on loans, partially offset by the $592.8 million, or 17.7% increase in the average total loan balance. Commercial loans were the primary driver of the average balance growth and yield decrease.
Compared to the first six months of 2019, interest and dividend income decreased $1.6 million, or 2.1%, reflecting similar trends as discussed in the quarter over quarter results. Average loans and loans held for sale increased $311.7 million, or 10.2%. As a result of a 39 basis point decrease in yield, there was a $1.1 million decrease in interest income on loans and loans held for sale.
Interest Expense. Interest expense decreased $4.4 million, or 61.2%, to $7.2 million for the three months ended June 30, 2020 from $11.6 million for the three months ended June 30, 2019. The decrease resulted from a $3.6 million decrease in interest expense on deposits and a $834,000 decrease in interest expense on FHLB borrowings. The decrease in interest expense on deposits reflected a 65 basis point decrease in the cost of interest bearing deposits, partially offset by $200.6 million, or 8.2%, increase in the average balance of interest-bearing deposits. Increases in the average balances were driven by organic growth. The decrease in cost of interest-bearing deposits was driven by rate decreases primarily in money market and certificate of deposit products and the resulting shift in balances to the savings product. The average balance of savings accounts increased $314.2 million, or 59.5%, and the average cost of savings accounts decreased 3 basis points. The cost of money market deposits decreased 97 basis points to 0.59% for the three months ended June 30, 2020 compared to the three months ended June 30, 2019 and the average balance decreased 5.2%. Average certificates of deposit decreased by $57.9 million, or 7.3%, and the cost of certificates of deposits was 1.91% for the second quarter of 2020 compared to 2.35% for the second quarter of 2019. The decrease in interest expense on FHLB advances resulted from a 100 basis point decrease in the cost of FHLB advances and a $33.2 million, or 11.4%, decrease in average balances.
Compared to the first six months of 2019, interest expense decreased $4.9 million, or 21.9% to $17.6 million from $22.6 million reflecting similar trends discussed in the quarter over quarter results. Average interest bearing deposits increased $219.1 million, or 9.2% and the cost of interest-bearing deposits decreased 36 basis points year over year. The decrease in interest expense on FHLB borrowings is due to a 64 basis point decrease in the cost of borrowed funds and the average balance decrease of $91.9 million, or 26.9%.
Net Interest and Dividend Income. Net interest and dividend income on a tax equivalent basis increased $2.7 million, or 10.1%, to $29.5 million for the three months ended June 30, 2020 from $26.7 million for the three months ended June 30, 2019, primarily as a result of deposit account repricing and commercial loan growth. The tax equivalent net interest spread decreased 16 basis points to 2.75% for the three months ended June 30, 2020 from 2.91% for the three months ended June 30, 2019, and net interest margin on a tax equivalent basis decreased 19 basis points to 3.00% for the three months ended June 30, 2020 from 3.19% for three months ended June 30, 2019.
Compared to the first six months of 2019, net interest and dividend income increased $3.4 million, or 6.4%, to $56.2 million from $52.8 million. The tax equivalent net interest spread decreased 25 basis points to 2.66% for the six months ended June 30, 2020 from 2.91% for the six months ended June 30, 2019, and net interest margin on a tax equivalent basis also decreased by 23 basis points to 2.96% for the six months ended June 30, 2020 from 3.19% for the six months ended June 30, 2019.
Income Tax Provision. The provision for income taxes and effective tax rate for the three months ended June 30, 2020 was $3.7 million and 25.8%, respectively, compared to $819,000 and 14.6%, respectively, for the three months ended June 30, 2019. Income tax expense for the quarter ended June 30, 2019 was impacted by the 2013 federal tax refund of $603,000 and the 2013 Massachusetts state tax refund of $211,000 recognized in the quarter.