In a matter of years, the share price of Nvidia (NVDA 1.92%) has made it one of the largest companies in the world, with a market cap that currently exceeds $3 trillion. Nvidia isn't alone, either. Many other AI stocks are exploding in value.

But is Nvidia stock still a buy? According to new research by The Motley Fool on AI adoption rates, the answer is a resounding yes. The statistics cited below could be surprising to many.

The AI revolution is just getting started

You're probably well aware of the AI craze occurring right now. But what you might not realize is that the revolution is just getting started. This is going to be a decades-long process, creating huge buying opportunities for early investors who remain patient. Just take a look at some of the adoption statistics compiled by The Fool in its recent report.

The current adoption rate of AI for U.S. business stands at just 6.8%. But the technology's projected usage rate over the next six months is 9.3% That's a 37% increase in just six months!

Yet even after that expected growth, total adoption of AI would remain under 10%. "Those numbers might appear low given how AI is often discussed as a game changer for businesses," the report reads. But that's exactly the point. For as much as artificial intelligence is talked about today, its actual adoption remains quite low. Rapid growth should change that story quickly, but this will take many years, if not decades, to fully play out.

The Fool isn't alone in its findings. According to research from global consultancy McKinsey, the AI market in 2040 will be tremendously larger than it is today. The numbers aren't even close.

The firm's low-end estimate has AI software and services revenue jumping from $85 billion in 2022 to $1.5 trillion in 2040. On the higher end, the industry's revenue could eventually reach $4.6 trillion!

Looking at generative AI alone, McKinsey expects $2.6 trillion to $4.4 trillion in added economic growth stemming from the technology's adoption by businesses.

This is going to be a growth opportunity like few others in history. But does that make a stock like Nvidia a buy right now? The answer may be surprising.

Is now the time to buy Nvidia?

Identifying a growth market is different than investing in one. That's because stocks with big potential are priced accordingly. So, while the underlying growth rate may be impressive, the valuation you pay for it may offset most of that growth.

Right now, Nvidia is in a curious position. For a multitrillion-dollar company, it's surprising to see its price-to-sales multiple (P/S) so high at 21.6. Yet its revenue is clearly on a huge growth trajectory. And given the statistics discussed above, it's reasonable to expect Nvidia to continue this for decades to come.

But is the stock a buy?

NVDA PS Ratio data by YCharts; TTM = trailing 12 months.

Growth stocks like Nvidia are notoriously volatile over the short term. Earlier this year, it had hundreds of billions of dollars shaved off its market cap due to an industrywide correction. A sudden rebound at any time is just as likely.

But investors seeking to capitalize on rising AI adoption rates shouldn't worry about short-term volatility. And due to Nvidia's dominance in AI graphic processing units -- fueled by early investments, strategic decisions like the 2006 launch of its CUDA developer suite, and a focus on controlling both the software and the hardware ends of the supply chain -- the company has the potential to sell into a rapidly growing market for many years to come. Over long stretches of time, even premium multiples can look cheap in hindsight.

Nvidia remains a great pick for investors looking to profit from the AI revolution. And patience will likely produce the biggest profits.