Even before the price dropped after the company’s investor day on Wednesday, the notoriously volatile shares recently hovered around $210, about half their November 2021 all-time high. Last year, the automaker delivered its best results by a mile as profits more than doubled to a record $12.6 billion. With factories in California, Nevada, Texas, New York, Germany, and China, the company produced almost 50% more vehicles last year than in the year before, and more factories are planned. All in all, it looks like a growth phenomenon for investors to grab hold of, and Wall Street analysts following the company agree, rating its stock “Buy” or “Overweight.” 

But a Fortune analysis suggests that while Tesla’s stock price has fallen dramatically from its high, it may not have fallen enough. 

Our analysis focuses on a company’s capital: how much capital it has, what it costs, and what it earns. The concept is simple. Take the return on a company’s total capital and subtract the cost of that capital. The result is what financial economists call economic profit, also known as economic value added (EVA). If it’s greater than zero, the company is creating wealth. Otherwise, it isn’t. Research has found that this method of analyzing companies is much more predictive than looking at earnings per share or EBITDA.

A similar Fortune analysis examined Amazon’s stock price in July 2021. It found that to justify the then-current share price of $180 a share (stated here to reflect a subsequent stock split), Amazon would have to increase its EVA by 11.8% a year for 20 years, which seemed unrealistic given the company’s mammoth size. Our conclusion: “The market may have stars in its eyes.” Yet of the 47 analysts following the stock, 43 rated it “buy” or “strong buy;” none rated it “sell.” They were all egregiously wrong. By the end of 2021, the stock had fallen to $150, and it has never returned to $180. It was recently at $92.

As with Amazon, Fortune‘s analysis of Tesla begins with the company’s EVA of $9.1 billion last year. So says ISS EVA, part of ISS Governance, which calculates EVA data for thousands of companies. That’s by far the highest EVA Tesla has ever achieved. Befitting a young, fast-growing business, Tesla produced negative EVAs for most of its existence, but that figure turned positive in 2020 and has risen since—precisely what investors hoped for.

The crucial question now is how fast Tesla can continue increasing its EVA. To find the answer, we asked ISS EVA to calculate the rate at which Tesla’s EVA would have to increase over the next 20 years to justify the recent stock price of $210. The result: 19.1% annually. 

Is that realistic? A 19.1% growth rate is entirely realistic for the next few years. After turning slightly positive in 2020, Tesla’s EVA increased by 1,195% in 2021 from a tiny base. Last year, it grew 121%. Those percentage increases are large and declining, which is expected as the company grows. 

But achieving a 19.1% compound annual growth rate over 20 years is another matter. Tesla would have to produce an EVA of $302 billion in the 20th year to do it. For perspective, consider that the largest EVA of any company in the S&P 500 is currently Apple’s $88.6 billion, says David Trainer, founder and CEO of the New Constructs research firm. Apple’s EVA has risen at a 7% compound annual growth rate over the past eight years, including a once-in-a-lifetime 71% leap in the pandemic year of 2021. The company’s EVA declined in three of the past eight years. Still, let’s make a highly optimistic assumption that Apple can continue increasing its EVA by 7% annually on average. At that rate, even with the highest EVA in the S&P, it would need 18 years to reach an EVA of $302 billion. 

Tesla’s recent stock price requires the company to get there in 20 years, starting from a dramatically lower base. Trainer says the stock price “implies they’re going to own never-before-seen market share percentages while maintaining margins higher than have ever been achieved.”

That seems like a long shot. Nonetheless, don’t be surprised if the share price goes up occasionally. Tesla’s stock is one of the most volatile among companies of its size, and sudden lurches up and down are likely. Day traders may find such swings exciting, but long-term investors shouldn’t be distracted.

At its recent stock price, Tesla is the world’s sixth most valuable company, slightly behind Berkshire Hathaway. Musk foresees the company overtaking all five companies ahead of it. He emailed Tesla employees in December, “Long term, I believe very much that Tesla will be the most valuable company on Earth!”

If he’s right, buying the stock now might work out well. If you don’t share his confidence, then proceed with caution.