of $16.3 million or 62.4%, compared to the six months ended June 30, 2020. Of this increase, $13.3 million relates to the mortgage segment as the number of employees in this segment have increased period over period.
Occupancy and equipment expense increased $275 thousand, or 13.4%, over the period due largely to the expansion of our physical office footprint into Maryland with 8 mortgage loan production offices having opened since early 2020. Professional fees were up $319 thousand, or 22.2%, over the period due to largely to a one-time consent fees related to the change in accountants early in 2021, not in 2020. This is combined with an increase in consulting fees as the bank continues to invest in various company-wide technology focused projects. Advertising and promotion expenses were up $493 thousand, or 40.6%, over the same period due to the improvements to the economy and a pull back on COVID-19 related restrictions that has allowed bank employees to spend more time in business development and community outreach capacity.
INCOME TAXES
Income tax expense for the three months ended June 30, 2021 was $2.5 million, as compared to $1.7 million for the same period in 2020. The increase in income tax expense was attributable to the increase in earnings, period over period. Our effective tax rate was 23.6% for the second quarter of 2021 and 22.8% for the second quarter of 2020.
Income tax expense for the six months ended June 30, 2021 was $5.7 million, as compared to $2.5 million, for the same periods in 2020. The increase in income tax expense was attributable to the increase in earnings, period over period. Our effective tax rate was 23.6% for the first six months of 2021 and 22.9% for the first six months of 2020.
BALANCE SHEET ANALYSIS
As of June 30, 2021, total assets were $1.7 billion, a decrease of $11.2 million from December 31, 2020. Total assets increased $129.9 million, or 8.2%, from June 30, 2020 primarily due to growth in loans held for investment and securities available-for-sale.
Total loans, net of allowance, grew $77.4 million, or 6.1%, to $1.3 billion as of June 30, 2021, from $1.3 billion as of December 31, 2020. There was growth in several commercial categories from December 31, 2020, as we continue to expand our presence in the Philadelphia market region. Commercial real estate loans increased $44.2 million, or 8.8%, small business loans increased $25.8 million, or 51.7%, and lease financings increased $35.4 million, or 107.2%, as our Meridian Equipment Finance (“MEF”) leasing team continued their strong growth pattern after starting up in early 2020. Residential mortgage loans held for sale decreased $96.9 million, or 42.3%, to $132.3 million as of June 30, 2021, while PPP loans decreased $13.7 million, or 6.9%, over this period.
The securities available-for-sale portfolio grew to $141.9 million as of June 30, 2021, up $18.3 million, or 14.8%, from December 31, 2020. This increase was driven by an increase of $9.4 million in state and municipal securities and $8 million in U.S. treasuries.
Servicing assets were $10.3 million as of June 30, 2021, up $4.7 million, or 83.8%, from December 31, 2020. $8.9 million of this balance is comprised of mortgage servicing rights, while $1.4 million is comprised of SBA loan servicing assets. The increase in both servicing asset types was the result of the continued strong loan sales markets since December 31, 2021.
Deposits were $1.4 billion as of June 30, 2021, up $171.9 million, or 13.9%, from December 31, 2020. Non-interest bearing deposits increased $58.0 million, or 28.4%, from December 31, 2020. Interest-bearing checking accounts increased $51.4 million, or 24.9%, from December 31, 2020, while money market accounts/savings accounts increased $59.0 million, or 10.3% since December 31, 2020. Increases in core deposits were driven from loan customers as part of new