Purchased Services and Other. Purchased services and other expense decreased $0.3 million, or 4.6%, to $5.8 million for the three months ended March 31, 2021, compared to the three months ended March 31, 2020. This decrease was primarily due to a decrease in professional services, consisting primarily of consulting and audit services, of $0.7 million, a decrease in office equipment expense of $0.1 million, a decrease in interrupted trip expense of $0.1 million, and a decrease in other miscellaneous expenses of $0.3 million. These decreases were offset by an increase in outside services, consisting primarily of line maintenance services, of $0.5 million, an increase in legal expenses of $0.1 million, and $0.3 million in gains on retirement of fixed assets.
Other (Expense) Income
Interest Income. Interest income increased $0.1 million, or 64.4%, to $0.4 million for the three months ended March 31, 2021, compared to the three months ended March 31, 2020. The increase was primarily due to an increase in interest earned on the long-term notes receivable from United.
Interest Expense. Interest expense decreased slightly to $0.4 million for the three months ended March 31, 2021, compared to the three months ended March 31, 2020 due to the repayment of debt in the year ended December 31, 2020. For additional information, refer to the section entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations – Debt and Credit Facilities” within our 2020 Annual Report.
Other (Expense) Income. Other expense decreased $0.02 million, or 100.0%, to $0.0 for the three months ended March 31, 2021, compared to the three months ended March 31, 2020.
Unrealized Loss on Marketable Securities. Unrealized loss on marketable securities was $0.06 million for the three months ended March 31, 2021. The loss reflects the change in market value of the securities as of the three months ended March 31, 2021. There were no marketable securities held during the three months ended March 31, 2020.
Net Income
Net income for the three months ended March 31, 2021 was $25.2 million, or $0.46 per basic share and $0.35 per diluted share, compared to net income of $4.4 million, earnings of $0.08 per basic share and earnings of $0.06 per diluted share for the three months ended March 31, 2020. For additional information, refer to Note 10, Earnings per Share, in our consolidated financial statements included in this Quarterly Report.
The net income for the three months ended March 31, 2021 primarily resulted from lower expenses as a result of the payroll support received under the Payroll Support Program, lower expenses related to reduced flying activity and lower aircraft rent expense due to Air Wisconsin owning its entire fleet of aircraft as of March 31, 2021, when compared to March 31, 2020.
Income Taxes
In the three months ended March 31, 2021, our effective tax rate was 24.0%, compared to (32.1)%, for the three months ended March 31, 2020. Our tax rate can vary depending on changes in tax laws, adoption of accounting standards, the amount of income we earn in each state and the state tax rate applicable to such income, as well as any valuation allowance required on our federal and state net operating losses.
We recorded an income tax expense of $8.0 million and an income tax benefit of $1.1 million for the three months ended March 31, 2021 and March 31, 2020, respectively.
The income tax expense for the three months ended March 31, 2021 resulted in an effective tax rate of 24.0%, which differed from the U.S. federal statutory rate of 21%, primarily due to the impact of state taxes and permanent differences between financial statement and taxable income.
The income tax provision for the three months ended March 31, 2020 resulted in an effective tax rate of (32.1)%, which differed from the U.S. federal statutory rate of 21%, primarily due to the impact of state taxes, the reversal of valuation allowances on federal and state deferred tax assets, and permanent differences between financial statement and taxable income, offset by a discrete tax benefit from a refund of alternative minimum tax credits available under a provision of the CARES Act that occurred during the period.
For additional information, refer to Note 5, Income Taxes, in our consolidated financial statements included within our 2020 Annual Report.
Liquidity and Capital Resources
The COVID-19 pandemic continues to evolve. As such, the ongoing impact that the COVID-19 pandemic will have on our financial condition, results of operations and liquidity is highly uncertain. Management is actively monitoring the impact on our operations, suppliers, industry, and workforce. We are taking actions based on currently available information to address the changing business environment; however, we cannot predict what changes in circumstances and future developments may occur or what effect those changes or developments may have on our business. The travel restrictions and other initiatives adopted to limit the spread of the virus have had, and will continue to have, a material adverse impact on the demand for air travel.
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