$248,420 for the comparable 2019 period. The decreases in both periods are a result of a decrease in frequency, primarily in our private passenger automobile line of business.
Our GAAP loss ratio for the three months ended June 30, 2020 decreased to 50.0% from 62.3% for the comparable 2019 period. Our GAAP loss ratio for the six months ended June 30, 2020 decreased to 55.7% from 63.5% for the comparable 2019 period. Our GAAP loss ratio excluding loss adjustment expenses for the three months ended June 30, 2020 was 41.2% compared to 53.4% for the comparable 2019 period. Our GAAP loss ratio excluding loss adjustment expenses for the six months ended June 30, 2020 was 46.7% compared to 54.9% for the comparable 2019 period. Total prior year favorable development included in the pre-tax results for the three months ended June 30, 2020 was $9,744 compared to $10,357 for the comparable 2019 period. Total prior year favorable development included in the pre-tax results for the six months ended June 30, 2020 was $19,328 compared to $22,337 for the comparable 2019 period.
Underwriting, Operating and Related Expenses. Underwriting, operating and related expenses for the three months ended June 30, 2020 increased by $2,606, or 4.3%, to $63,514 from $60,908 for the comparable 2019 period. Underwriting, operating and related expenses for the six months ended June 30, 2020 increased by $5,254, or 4.3%, to $126,596 from $121,342 for the comparable 2019 period. Our GAAP expense ratio for the three months ended June 30, 2020 increased to 34.9% from 31.0% for the comparable 2019 period. Our GAAP expense ratio for the six months ended June 30, 2020 increased to 33.3% from 31.0% for the comparable 2019 period. The increases in both periods are partially driven by costs associated with various system modernization in our claims, billing and underwriting areas, a reduction in certain expense allowances offered under the Servicing Carrier program that have decreased with the related written premium as noted above and an increase in contingent commission expense. Furthermore, the increases in the expense ratio in both periods reflect a lower earned premium base in the ratio calculation due to the premium relief efforts noted above.
Interest Expense. Interest expense was $130 for the three months ended June 30, 2020 compared to $23 for the comparable 2019 period. Interest expense was $177 for the six months ended June 30, 2020 compared to $45 for the comparable 2019 period. The credit facility commitment fee included in interest expense was $37 for the six months ended June 30, 2020 and 2019.
Income Tax Expense. Our effective tax rate was 20.1% and 20.6% for the three months ended June 30, 2020 and 2019, respectively. Our effective tax rate was 19.5% and 18.7% for the six months ended June 30, 2020 and 2019. The effective tax rates for the three and six months ended June 30, 2020 were lower than the statutory rate primarily due to the effects of tax-exempt investment income and the impact of stock-based compensation. The effective tax rates for the three and six months ended June 30, 2019 were lower than the statutory rate primarily due to the effects of tax-exempt investment income.
Net Income. Net income for the three months ended June 30, 2020 was $42,494 compared to net income of $25,934 for the comparable 2019 period. Net income for the six months ended June 30, 2020 was $40,504 compared to net income of $55,880 for the comparable 2019 period. The increase in both periods is a result of a decrease in loss and loss adjustment expenses as described above.
Non-GAAP Operating Income. Non-GAAP operating income as defined above was $29,739 for the three months ended June 30, 2020 compared to $22,629 for the comparable 2019 period. Non-GAAP operating income was $53,921 for the six months ended June 30, 2020 compared to $43,556 for the comparable 2019 period.
Liquidity and Capital Resources
As a holding company, Safety’s assets consist primarily of the stock of our direct and indirect subsidiaries. Our principal source of funds to meet our obligations and pay dividends to shareholders, therefore, is dividends and other permitted payments from our subsidiaries, principally Safety Insurance. Safety is the borrower under our credit facility.