Though artificial intelligence has been the hottest trend on Wall Street, it’s far from the only catalyst responsible for sending the benchmark S&P 500 (^GSPC -0.13%) to new heights. Investor excitement surrounding stock splits in high-profile businesses has played a close second fiddle.

A stock split allows a publicly traded company to cosmetically adjust its share price and outstanding share count by the same factor. These changes are “cosmetic” in the sense that they don’t impact a company’s market cap or its operating performance.

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Typically, investors keep their distance from businesses enacting reverse splits and gravitate to those announcing and completing forward splits. The latter is designed to lower a company’s share price to make it more nominally affordable for retail investors who can’t buy fractional shares through their broker. Companies that complete forward splits are usually out-innovating and out-executing their competition.

As of the closing bell on Sept. 12, three magnificent businesses had announced and completed forward splits this year. Whereas the benchmark S&P 500 has risen by roughly 12% on a year-to-date (YTD) basis, Wall Street’s trio of stock-split stocks has crushed it!

O’Reilly Automotive: up 36% YTD

Though it wasn’t the first to complete its split, auto parts supplier O’Reilly Automotive (ORLY -0.85%) kicked off stock-split euphoria in 2025 by announcing its intent to conduct a 15-for-1 forward split in mid-March. O’Reilly sought shareholder approval for its largest-ever stock split and was granted it, which paved the way for its split taking effect before the opening bell on June 10.

While shares of the company have jumped 36% on a year-to-date basis, they’re up closer to 67,000% since its initial public offering (IPO) in 1993.

O’Reilly Automotive has a few important tailwinds working in its favor. On a macro basis, S&P Global Mobility recently reported that the average age of vehicles on U.S. roadways jumped to 12.8 years in 2025. For context, this is up from an average of 11.1 years in 2012. With consumers hanging onto their cars and light trucks longer than ever before, they and their mechanics will be turning to auto parts retailers like O’Reilly to keep these vehicles in tip-top shape.

Additionally, O’Reilly has reworked its distribution system to ensure that drivers and mechanics have access to the parts they need. O’Reilly entered the year with 31 distribution centers and close to 400 hub stores. These hub stores feed from the distribution centers and ensure that outlying retail locations have access to more than 153,000 stock keeping units (SKUs) delivered same-day or on an overnight basis.

From an investment standpoint, O’Reilly’s greatest gift might just be its stellar capital-return program. Since initiating a share repurchase program in January 2011, O’Reilly has spent $26.6 billion to buy back almost 60% of its outstanding shares. For companies with steady or growing net income, buybacks can provide a big boost to earnings per share (EPS).

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Fastenal: up 32% YTD

A second stock-split stock that’s come close to tripling the year-to-date return of the broad-based S&P 500 is wholesale industrial and construction supplies company Fastenal (FAST -1.07%). Shares are up 32% YTD, but more than 150,000% since its August 1987 IPO.

Stock splits might as well be part of Fastenal’s corporate culture. The 2-for-1 split that was announced in April and effected prior to the start of trading on May 22 marked the ninth time in 37 years Fastenal had completed a split.

Fastenal is a company that benefits immensely from the disproportionate nature of economic cycles. This is to say that while economic downturns are normal, healthy, and inevitable, they tend to be short-lived. The average economic expansion since the end of World War II has stuck around five years, which is fantastic news for a company whose growth tends to ebb-and-flow with the health of the U.S. economy and cyclical industries.

Fastenal’s ongoing success is also reflective of its closeknit ties to its most-promising clients. During the second quarter, more than 73% of its net revenue traced back to contract sales, which are multisite, local, regional, and government customers that offer significant revenue potential. Being able to place its inventory solutions on-site helps integrate Fastenal’s products into the supply chains of its most important customers.

Lastly, innovation has been key to Fastenal’s six-digit percentage rally since its debut. The company’s managed inventory solutions, such as its internet-connected wireless vending machines and inventory tracking bins, help its clients save money and ensures that Fastenal has a good bead on the supply chain needs of its customers.

Interactive Brokers Group: up 44% YTD

However, the top-performer among stock-split stocks in 2025 is automated electronic brokerage firm Interactive Brokers Group (IBKR 0.45%), which has rallied 44% YTD and 438% over the trailing half-decade.

Unlike O’Reilly Automotive and Fastenal, Interactive Brokers made history when it completed a 4-for-1 forward split before the opening bell on June 18. This marked its first split since becoming a public company in May 2007.

One of the top tailwinds for Interactive Brokers Group is the stock market being in an uptrend. When the S&P 500 is hitting new highs, investors have a tendency to want in on the action. This typically means trading more, adding more money to the platform, and potentially using margin. Bull markets for the S&P 500 often create an excellent operating environment for Interactive Brokers.

Another factor fueling this outperformance is the company’s investments in technology and automation. Though these investments came at a cost, they’re allowing Interactive Brokers to offer higher interest rates to customers on cash kept in their accounts, as well as lower borrowing rates for margin. These are attractive perks that are clearly resonating with investors.

The final piece of the puzzle is that every meaningful key performance indicator for Interactive Brokers is pointing significantly higher. During the June-ended quarter, customer accounts and customer equity on the platform jumped 32% and 34%, respectively, with daily active revenue trades (a measure of trading activity on the platform) climbing 49%! It’s not hard to see why Interactive Brokers Group is leading the way in 2025.