This Stock Grew About 500% in the Past 5 Years. And No, It's Not an AI Stock.

There is a good chance you've never thought of Interactive Brokers (NASDAQ: IBKR) as a high-growth stock.

That may be exactly why its performance is so interesting. During the past five years, Interactive Brokers' stock has gained nearly 500%, rising from about $15 to $93 (as of Aug. 24).

Interactive Brokers isn't an artificial intelligence (AI) stock. It doesn't make graphics processing units (GPUs). It doesn't build large language models. It doesn't run data centers. It operates an online brokerage.

So how did a financial service company that rarely dominates headlines produce a return that would make many technology investors jealous?

Image source: Getty Images.

The business has been quietly growing over the years

Interactive Brokers may not appear to be a growth stock, but that doesn't stop the company from growing. Let's start with customer growth.

At the end of 2025, Interactive Brokers had about 4.4 million customer accounts. By the second quarter of 2026, that number had reached 5.19 million -- a 34% increase from a year earlier. Customer equity reached $930.3 billion, up 40%, while daily average revenue trades increased 36% to 4.82 million.

But the company hasn't just been increasing its customer base recently. By the end of 2021, it had only 1.7 million customer accounts and $374 billion in customer equity. So across almost every important metric, the company has been improving over the years.

Those numbers demonstrate that Interactive Brokers isn't simply a brokerage collecting commissions from the same customers year after year. It is adding customers rapidly, attracting more assets, and increasing activity across the platform.

And because its infrastructure is highly automated, the economics of that growth can be unusually attractive. For perspective, revenue grew by 126% between 2021 and 2025, while net income more than tripled during the same period.

That's the beauty of operating leverage: When revenue grows faster than expenses, more of each additional dollar can reach the bottom line. That's the first reason the stock has compounded so quickly.

The market began to see a different kind of broker

The second reason is more subtle.

For years, investors could reasonably put Interactive Brokers in the same broad category as other online brokers. But the company's economics increasingly made that comparison less useful.

Interactive Brokers provides access to more than 170 markets across 40 countries and 29 currencies. Customers can trade stocks, options, futures, currencies, bonds, funds, and other products on a single platform.

That breadth matters because it creates a powerful combination: More customers means more assets, which invites more activity, which generates more revenue, which drives more operating leverage.

The company also doesn't need every customer to be a high-frequency trader. A customer who brings substantial assets to the platform can generate value through multiple channels, including trading, margin lending, cash balances, and other services.

That makes the customer relationship more valuable than a simple commission transaction. And investors, unsurprisingly, rewarded the company with a higher valuation. Five years ago, the stock traded at roughly an 18 to 20 price-to-earnings (P/E) ratio. Today, it trades at a P/E of 37.

But can the next five years look anything like the last five?

This is where the investment story becomes much harder. A 500% gain creates a dangerous temptation: extrapolation.

Investors may look at the past five years and assume another 500% is possible simply because the business is still growing rapidly.

But here's the thing. The stock price has already moved dramatically, and the valuation is much higher than it was five years ago. That means the next leg of the investment case will increasingly depend on earnings growth, rather than on investors simply discovering the company and assigning it a higher valuation.

Fortunately, the runway isn't necessarily finished. If Interactive Brokers can continue to expand its customer base, client assets, and trading activity while preserving its exceptional cost structure, earnings can continue to compound. That's what investors should watch.

What does it mean for investors?

Interactive Brokers' 500% five-year return isn't about riding an AI story. It is an example of quiet compounding.

The company kept adding customers. Those customers brought more assets. More assets generated more activity and revenue. And the company's automated infrastructure enabled a large portion of that growth to translate into profit.

But the biggest mistake investors can make now is assuming that the stock's past performance guarantees its future. It doesn't. The easy part may already be behind us. From here, the business has to earn its way into a higher valuation.

Still, if the company continues to compound its earnings at anything close to its historical pace, the stock price can continue to rise.

Lawrence Nga has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Interactive Brokers Group. The Motley Fool recommends the following options: long January 2027 $43.75 calls on Interactive Brokers Group and short January 2027 $46.25 calls on Interactive Brokers Group. The Motley Fool has a disclosure policy.