Our GAAP loss ratio for the three months ended September 30, 2023 increased to 74.4% from 65.3% for the comparable 2022 period. Our GAAP loss ratio for the nine months ended September 30, 2023 increased to 77.3% from 63.7% for the comparable 2022 period. Our GAAP loss ratio excluding loss adjustment expenses for the three months ended September 30, 2023 was 65.7% compared to 53.5% for the comparable 2022 period. Our GAAP loss ratio excluding loss adjustment expenses for the nine months ended September 30, 2023 was 67.8% compared to 54.6% for the comparable 2022 period. Total prior year favorable development included in the pre-tax results for the three months ended September 30, 2023 was $13,476 compared to $13,950 for the comparable 2022 period. Total prior year favorable development included in the pre-tax results for the nine months ended September 30, 2023 was $34,997 compared to $43,223 for the comparable 2022 period. The decrease in the prior year favorable development in 2023 is primarily related to the reversal of $6,500 legal expense reserve during the second quarter of 2022.
Underwriting, Operating and Related Expenses. Underwriting, operating and related expenses for the three months ended September 30, 2023 increased by $4,844, or 8.0%, to $65,217 from $60,373 for the comparable 2022 period. Underwriting, operating and related expenses for the nine months ended September 30, 2023 increased by $4,993, or 2.7%, to $187,832 from $182,839 for the comparable 2022 period. The increase in the three months and nine months ended September 30, 2023 is driven by an increase in base commissions resulting from the increase in written premiums, offset by a decrease in contingent commission expenses. Our GAAP expense ratio for the three months ended September 30, 2023 decreased to 30.4% from 31.8% for the comparable 2022 period. Our GAAP expense ratio for the nine months ended September 30, 2023 decreased to 30.9% from 32.3% for the comparable 2022 period.
Interest Expense. Interest expense was $139 and $132 for the three months ended September 30, 2023 and 2022, respectively. Interest expense was $697 for the nine months ended September 30, 2023 compared to $392 for the comparable 2022 period. The credit facility commitment fee included in interest expense was $37 for the nine months ended September 30, 2023 and 2022. The increase in interest expense is due to higher interest rates on outstanding debt in 2023.
Income Tax Expense. Our effective tax rate was 21.3% and 20.3% for the three months ended September 30, 2023 and 2022, respectively. The effective tax rate was 23.4% and 21.0% for the nine months ended September 30, 2023 and 2022, respectively. The effective tax rate in 2023 was higher primarily due to the effects of the change in unrealized gains on equity securities and the impact of stock-based compensation.
Net Income. Net income for the three months ended September 30, 2023 was $1,949 compared to net income of $6,192 for the comparable 2022 period. Net income for the nine months ended September 30, 2023 was $6,613 compared to net income of $21,931 for the comparable 2022 period.
Non-GAAP Operating Income. Non-GAAP operating income, as defined above, was $8,673 for the three months ended September 30, 2023 compared to $16,715 for the comparable 2022 period. Non-GAAP operating income was $7,870 for the nine months ended September 30, 2023 compared to $59,754 for the comparable 2022 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.
Safety Insurance’s sources of funds primarily include premiums received, investment income, and proceeds from sales and redemptions of investments. Safety Insurance’s principal uses of cash are the payment of claims, operating expenses and taxes, the purchase of investments, and the payment of dividends to Safety.
Net cash provided by operating activities was $17,063 and $23,366 during the nine months ended 2023 and 2022, respectively. Our operations typically generate positive cash flows from operations as most premiums are received in advance of the time when claim and benefit payments are required. Positive operating cash flows are expected in the future to meet our liquidity requirements.