Nvidia, the world’s largest maker of AI chips, led to a global stock market decline on Wednesday, with indexes falling in Asia, Europe and the United States.

After news broke on Tuesday that the U.S. Department of Justice had sent Nvidia a subpoena as part of an antitrust investigation, investors sold $279 billion worth of stock, representing 9.5 percent of the company’s shares. The sell-off is bad news for Nvidia and has rekindled concerns about the strength of the AI ​​sector and the U.S. economy overall.

That one company could have such an impact on global stock prices is a testament to Nvidia’s size and reach. Nvidia is the world’s third-most valuable company. Because of its dominance, its success — or failure — can shift the tech-heavy Nasdaq stock index where it’s listed. And because it’s so intertwined with other tech companies, shares of its affiliates, such as Taiwan Semiconductor Manufacturing Company, have also fallen, dragging down markets abroad. In the U.S., Nvidia fueled a selloff across the tech industry. Microsoft, Amazon and Intel shares were down Wednesday afternoon, though Nvidia rival Advanced Micro Devices posted gains.

“One of the big risks is that you have this market concentration, and all it takes is for those names to be volatile for it to filter through to the entire market,” Justin Onuekwusi, chief investment officer at investment firm St. James’s Place, told Reuters on Wednesday.

While Nvidia may have caused this week’s stock market decline, there are a few other factors rattling investors. Recent concerns about China’s sluggish economy are putting a damper on a wide range of companies, including an oil industry already struggling with falling prices. Weak U.S. manufacturing, along with somewhat higher prices in that sector, are also part of the equation.

Investors are deeply concerned about whether the U.S. tech sector is headed in the right direction. Questions about whether Nvidia is overvalued and whether it’s wise to invest so heavily in AI technology have dogged the tech sector for months. Analysts at JPMorgan Asset Management and Blackrock warned earlier this week that massive spending on AI is unwarranted because the technology has limited applications outside of tech.

Companies like Microsoft and Meta have ignored that advice, spending as much as 40 percent of their hardware budgets — tens of billions of dollars — on Nvidia products to accelerate their own AI products. But that has investors worried that tech companies are betting too much on a future that may never come. And that if these giant companies make a bad bet, they could drag the stock market down with them.

“(Tech companies) are all saying, ‘Look, we’re not going to get on the wrong side of this. We’re going to invest,’” Daniel Newman, CEO of Futurum Group, a global technology research and advisory firm, told Vox. “But I’m not hearing what, or where the return is. And I think there’s a little bit of hesitation on (Wall Street) — people want to know where that return is going to come from.”

All of this — from concerns about China’s economy to the strategy of tech companies — comes as some financial and economic experts are warning that the U.S. is in danger of a recession. And this week’s unrest has only reinforced concerns that those experts may be right.

There is no doubt that Wednesday’s sell-off is worrying, but it is not yet clear whether it says anything about the risk of a recession.

Stock market performance isn’t the only — or even the best — indicator of economic health. Stocks rebounded from last month’s volatile early selloff on news that the Federal Reserve would cut interest rates, make credit cheaper and hopefully make it easier for people to make big purchases and for companies to hire employees and make other investments.

The Fed is expected to cut interest rates by a quarter point at its meeting this month, which could help ease some recession fears. But that alone is unlikely to eliminate those worries entirely.

While the US is not currently in a recession (traditionally defined as negative gross domestic product growth for two consecutive quarters), there are concerns that a recession could still occur due to high inflation and high interest rates, which could limit output and lead to higher unemployment rates.

Nvidia’s fall this week probably isn’t the ultimate indicator of whether the economy is headed into a recession, and it may not even last that long. But it does say something about the markets’ reliance on the tech sector — and it’s just the latest reminder of how much uncertainty remains around the U.S. economy.