This Buffett Stock Has Crushed the Market During the Past 5 Years. Here's Why It's Still a Buy Today.

Under Warren Buffett's watch, Berkshire Hathaway built up a position in American Express (NYSE: AXP) worth more than $53 billion today, or 22.1% of all shares outstanding. That stake accounts for 16.4% of the entire Berkshire Hathaway equity portfolio, making it the second-largest position after Apple.

Buffett has sung the company's praises many times, pointing out its global brand and dividend, and it fits the typical Buffett schema in multiple ways: it plays a large role in the economy, it's cash-rich, and it's a leader in its market. None of that has changed, which is why it has always remained a major component of the Buffett portfolio and why it's still a buy today.

Image source: American Express.

Investing for the future

Not only has the model not changed, but American Express is as strong as ever, and it continues to invest in its business and competitive advantage to protect its moat and stay on top of the financial services industry. It has carved out a niche serving an affluent clientele, and on the fourth-quarter earnings call, Chief Executive Officer Stephen Squeri noted the company's investments as a key feature in its success. He said that in each area where it has focused its investments, the company can point to direct, positive results.

American Express spent $6.3 billion in marketing in 2025, a 75% increase since 2019, and it sees the results in multiple ways, including higher customer demand and engagement, improved credit quality, and stronger retention and relationship expansion. It invests in two general areas, maintenance and innovation. Technology is an important piece of the approach, and it's rolling out a new cloud-based data analytics model for deeper personalization in its marketing, leading to better expected results.

Showing up in the results

American Express demonstrated robust growth in the 2025 fourth quarter, with a 10% year-over-year increase in revenue and a 16% increase in earnings per share (EPS). Card fees increased 17% year over year, and the company didn't have any decrease in renewal rates despite a card refresh with increased annual fees.

Its model is resonating with younger consumers. Gen-Z spending accounted for only 6% of the total, the smallest of any age group, but also grew 36% year over year -- the fastest of any age group. That points to a long growth runway as this group ages, which is why American Express is such a timeless company.

American Express stock has crushed the S&P 500 (SNPINDEX: ^GSPC) during the past five years as its business has thrived, up 201% versus 91% for the broader index. Expect that to continue as the company invests for the future and captures market share among younger consumers.

American Express is an advertising partner of Motley Fool Money. Jennifer Saibil has positions in American Express and Apple. The Motley Fool has positions in and recommends Apple and Berkshire Hathaway. The Motley Fool has a disclosure policy.