want to congratulate Team O’Reilly on their consistent performance and unwavering commitment to our customers. Our Team also delivered a strong finish to our expansion efforts in 2024, meeting our new store opening target with the successful opening of 198 net, new stores and completing our planned distribution expansion with the relocation of our Atlanta, Georgia distribution center to a larger, modern facility in the fourth quarter.”
Sales for the year ended December 31, 2024, increased $896 million, or 6%, to $16.71 billion from $15.81 billion for the same period one year ago. Gross profit for the year ended December 31, 2024, increased 6% to $8.55 billion (or 51.2% of sales) from $8.10 billion (or 51.3% of sales) for the same period one year ago. SG&A for the year ended December 31, 2024, increased 8% to $5.30 billion (or 31.7% of sales) from $4.92 billion (or 31.1% of sales) for the same period one year ago. Operating income for the year ended December 31, 2024, increased 2% to $3.25 billion (or 19.5% of sales) from $3.19 billion (or 20.2% of sales) for the same period one year ago.
Net income for the year ended December 31, 2024, increased $40 million, or 2%, to $2.39 billion (or 14.3% of sales) from $2.35 billion (or 14.8% of sales) for the same period one year ago. Diluted earnings per common share for the year ended December 31, 2024, increased 6% to $40.66 on 59 million shares versus $38.47 on 61 million shares for the same period one year ago.
4th Quarter and Full-Year Comparable Store Sales Results
Comparable store sales are calculated based on the change in sales for U.S. stores open at least one year and exclude sales of specialty machinery, sales to independent parts stores, and sales to Team Members, as well as sales from Leap Day for the year ended December 31, 2024. Online sales for ship-to-home orders and pick-up-in-store orders for U.S. stores open at least one year are included in the comparable store sales calculation. Comparable store sales increased 4.4% for the fourth quarter ended December 31, 2024, on top of 3.4% for the same period one year ago. Comparable store sales increased 2.9% for the year ended December 31, 2024, on top of 7.9% for the same period one year ago.
Share Repurchase Program
During the fourth quarter ended December 31, 2024, the Company repurchased 0.4 million shares of its common stock, at an average price per share of $1,207.43, for a total investment of $472 million. During the year ended December 31, 2024, the Company repurchased 1.9 million shares of its common stock, at an average price per share of $1,072.47, for a total investment of $2.08 billion. Excise tax on shares repurchased, assessed at one percent of the fair market value of shares repurchased, was $20.8 million for the year ended December 31, 2024. Subsequent to the end of the fourth quarter and through the date of this release, the Company repurchased an additional 0.1 million shares of its common stock, at an average price per share of $1,232.37, for a total investment of $181 million. The Company has repurchased a total of 96.2 million shares of its common stock under its share repurchase program since the inception of the program in January of 2011 and through the date of this release, at an average price of $264.49, for a total aggregate investment of $25.44 billion. As of the date of this release, the Company had approximately $2.31 billion remaining under its current share repurchase authorizations.