sales for the three months ended March 31, 2022, was primarily due to the impact from the rollout of our professional pricing initiative, which was a strategic investment aimed at ensuring we are more competitively priced on the professional side of our business, and a greater percentage of our total sales mix generated from professional service provider customers, which carry a lower gross margin than DIY sales.
Selling, general and administrative expenses:
Selling, general and administrative expenses (“SG&A”) for the three months ended March 31, 2022, increased 9% to $1.04 billion (or 31.5% of sales) from $950 million (or 30.7% of sales) for the same period one year ago. The increase in total SG&A dollars for the three months ended March 31, 2022, was the result of additional Team Members, facilities and vehicles to support our increased sales and store count. The increase in SG&A as a percentage of sales for the three months ended March 31, 2022, was primarily due to inflationary pressures on wages, benefits and fuel costs and increased payroll, as compared to the same period one year ago, when store payroll hours were constrained due to expense control measures in response to the pandemic and the difficult labor environment.
Operating income:
As a result of the impacts discussed above, operating income for the three months ended March 31, 2022, decreased 3% to $670 million (or 20.3% of sales) from $691 million (or 22.4% of sales) for the same period one year ago.
Other income and expense:
Total other expense for the three months ended March 31, 2022, increased 3% to $36 million (or 1.1% of sales) from $35 million (or 1.1% of sales) for the same period one year ago. The increase in total other expense for the three months ended March 31, 2022, was the result of a decrease in the value of our trading securities, partially offset by decreased interest expense on lower average outstanding borrowings.
Income taxes:
Our provision for income taxes for the three months ended March 31, 2022, decreased 2% to $151 million (23.9% effective tax rate) from $154 million (23.5% effective tax rate) for the same period one year ago. The decrease in our provision for income taxes for the three months ended March 31, 2022, was the result of lower taxable income, partially offset by lower excess tax benefits from share-based compensation. The increase in our effective tax rate for the three months ended March 31, 2022, was the result of lower excess tax benefits from share-based compensation.
Net income:
As a result of the impacts discussed above, net income for the three months ended March 31, 2022, decreased 4% to $482 million (or 14.6% of sales) from $502 million (or 16.2% of sales) for the same period one year ago.
Earnings per share:
Our diluted earnings per common share for the three months ended March 31, 2022, increased 2% to $7.17 on 67 million shares from $7.06 on 71 million shares for the same period one year ago.
LIQUIDITY AND CAPITAL RESOURCES
Our long-term business strategy requires capital to open new stores, fund strategic acquisitions, expand distribution infrastructure, operate and maintain our existing stores and may include the opportunistic repurchase of shares of our common stock through our Board-approved share repurchase program. Our material cash requirements necessary to maintain the current operations of our long-term business strategy include, but are not limited to, inventory purchases, human capital obligations, including payroll and benefits, contractual obligations, including debt and interest obligations, capital expenditures, payment of income taxes and other operational priorities. We expect to fund our short- and long-term cash and capital requirements with our primary sources of liquidity, which include funds generated from the normal course of our business operations and borrowings under our unsecured revolving credit facility. However, there can be no assurance that we will continue to generate cash flows or maintain liquidity at or above recent levels, as we are unable to predict decreased demand for our products, changes in customer buying patterns or the impact of the uncertainty and disruption caused by the COVID-19 pandemic. Additionally, these factors could also impact our ability to meet the debt covenants of our credit agreement and, therefore, negatively impact the funds available under our unsecured revolving credit facility.
There have been no material changes to the contractual obligations, to which we are committed, since those discussed in our Annual Report on Form 10-K for the year ended December 31, 2021.