On August 1, popular burger chain ShakeShack (SCHA -1.94%) reported financial results for the second quarter of the fiscal year and reported revenue growth of 16%, almost as good as the 18% revenue growth Chipotle Mexican Grill (CMG -2.78%) reported in the second quarter.

That’s normal. The two chains have grown at a similar pace over the past five years, with Shake Shack slightly outpacing Chipotle. But if you invested $1,000 in Chipotle stock five years ago, you’d have nearly $3,200 today. If you’d done the same with Shake Shack stock, you’d have just $1,100 today.

Sales growth is one one of the most important things to look for when investing in stocks, but it’s far from the only one. And one chart shows why Shake Shack’s growth hasn’t made its shareholders as rich as Chipotle’s investors.

The chart you have to see to believe

When companies go public, they sell shares to investors to raise capital. But after that, the number of shares changes. Companies can issue new shares to raise more money or pay employees, which increases the number of shares issued. And these companies can also use profits to buy back shares from investors, which decreases the number of shares issued.

Chipotle has slightly reduced its share count over the past five years, while Shake Shack’s share count has increased dramatically. So while Shake Shack’s sales have more than doubled, per share has only increased by about 50%.

Data from YCharts.

There is no way to know for sure, but if Shake Shack’s share count had remained stable or even declined over the past five years, I would bet that the stock would S&P500 during this time. After all, the company’s growth has been outstanding. But the increasing share count has diluted the value for shareholders and negated much of the positive impact of the sales.

And what about the next five years?

The good news for Shake Shack shareholders is that things could change in the next five years. The company offers stock-based compensation to its executives to better connect them with the company. But much of what has happened in the past has been related to an incentive plan introduced in 2015, and things are slowing down.

In the last quarter, Shake Shack’s diluted share count actually decreased compared to the previous year. Admittedly, management did not reduce the number of shares through share buybacks. Rather, part of the potential compensation was lost.

Still, it does suggest that Shake Shack is starting to turn things around in this regard, meaning that revenue per share growth could soon be more in line with actual revenue growth. That could be a big deal.

As I mentioned, sales growth is important for stocks. Shake Shack is experiencing tremendous growth—it opened nearly 80 new stores last year, many of which it owns. Sales could continue to grow at double-digit rates for years to come.

In addition, Shake Shack is profitable, another important factor in a stock’s performance. The company had operating income of nearly $11 million in its fiscal second quarter. And with ongoing investments in technology to keep labor costs under control, that number should continue to rise.

To be clear, I personally am not willing to give Shake Shack the benefit of the doubt. Investors can afford to be patient for now and wait to see if recent trends continue. But I am willing to keep a closer eye on the business going forward, as the company’s growth could finally lead to better rewards for shareholders in the years to come.