unfavorable net prior year loss reserve development. Decreased revenue for the first half of 2021 compared to the same period of the prior year was due primarily to decreased net premiums earned of $46.7 million, lower net investment income of $2.3 million and lower finance charges of $1.0 million, partially offset by $36.9 million higher net investment gains.
Loss and Loss Adjustment Expenses (“LAE”) and Net Combined Ratios
Losses and LAE for the three and six months ended June 30, 2021 decreased $17.2 million and $39.7 million, as compared to the same periods during 2020 due to improved prior year net loss reserve development, lower net catastrophe losses and lower net premiums earned, partially offset by increases in current accident year non-catastrophe net loss trends. There was $3.1 million and $1.0 million of net unfavorable prior year loss reserve development during the three and six months ended June 30, 2021 as compared to net unfavorable prior year loss reserve development of $10.8 million and $19.3 million during the same periods in 2020. Net catastrophe losses were $3.7 million and $9.6 million during the three and six months ended June 30, 2021 as compared to $6.6 million and $12.6 million, during the same periods of 2020.
The net loss ratio was 78.8% and 73.3% for the three and six months ended June 30, 2021, as compared to 75.5% and 75.5% reported during the same periods in 2020. Catastrophe losses contributed 3.8 points and 4.8 points to the net loss ratio for the three and six months ended June 30, 2021, as compared to 5.2 points and 5.0 points for the same periods during 2020. Net unfavorable prior year loss reserve development contributed 3.2 points and 0.5 points to the net loss ratio for the three and six months ended June 30, 2021, as compared to 8.6 points and 7.8 points contributed to the net loss ratio from net unfavorable prior year loss reserve development for the same periods during 2020.
The expense ratio was 26.9% and 27.5% for the three and six months ended June 30, 2021, as compared to 22.9% and 22.5% during the same periods in 2020. The Company reported net combined ratios of 105.7% and 100.8% for the three and six months ended June 30, 2021, as compared to 98.4% and 98.0% for the same periods during 2020.
Net Income (Loss)
Net loss was $0.5 million and net income was $8.9 million for the three and six months ended June 30, 2021, as compared to net income of $6.7 million and a net loss of $57.6 million for the same periods during 2020.
On a diluted basis per share, net loss was $0.03 per share and net income was $0.49 per share for the three and six months ended June 30, 2021, as compared to net income of $0.37 per share and net loss of $3.18 per share for the same periods in 2020.
Book Value Per Share
Book value per share increased 4% to $9.84 per share as of June 30, 2021 as compared to $9.42 per share as of December 31, 2020.
Non-GAAP Financial Measures
The Company’s financial statements are prepared in accordance with United States generally accepted accounting principles (“GAAP”). However, the Company also presents and discusses certain non-GAAP financial measures that it believes are useful to investors as measures of operating performance. Management may also use such non-GAAP financial measures in evaluating the effectiveness of business strategies and for planning and budgeting purposes. However, these non-GAAP financial measures should not be viewed as an alternative or substitute for the results reflected in the Company’s GAAP financial statements. In addition, the Company’s definitions of these items may not be comparable to the definitions used by other companies.
Operating loss and operating loss per share are calculated by excluding net investment gains and losses and impairment of goodwill and other intangible assets (“Impairments”) from GAAP net income. The Impairments are unusual and infrequent charges for the Company. Management believes that operating earnings and operating earnings per share provide useful information to investors about the performance of and underlying trends in the Company’s core insurance operations. Net income and net income per share are the GAAP