Warren Buffett’s Red Warning Siren Has Rarely Been Louder

With investor enthusiasm driving U.S. equities to record highs and concerns about overexcitement and “bubbles,” an indicator devised by acclaimed investor Warren Buffett is sounding alarms about the U.S. economy’s trajectory.

Named after the former Berkshire Hathaway CEO, the “Buffett Indicator” weighs the value of publicly traded stocks against an economy’s output, and has been widely employed as a gauge of potential over- or undervaluation in the stock market.

The indicator is currently sitting at well over 200 percent—according to the websites LongTermTrends and MacroMicro—a threshold Buffett once said meant investors were “playing with fire.”

What Is the Buffett Indicator?

Buffett’s metric first appeared in a 2001 Fortune piece, in which the “Oracle of Omaha” argued it could reliably measure whether the stock market is overvalued or undervalued relative to the size of the wider economy at a given time.

Though several variations have been proposed, the original indicator takes the value of all publicly traded securities in the United States and divides it by the nation’s Gross National Product (GNP), expressing the result as a percentage. Buffett said that the figure could function as a yardstick for market valuation.

However, Buffett said this could also signal a coming correction or crash, and a buying opportunity if it declines significantly.

“If the percentage relationship falls to the 70 percent or 80 percent area, buying stocks is likely to work very well for you,” Buffett wrote.

However, he added that as the ratio approaches 200 percent, the chances increase that investors are “playing with fire,” noting that this occurred in 1999 and 2000 ahead of the dot-com bubble bursting—a downturn often linked to the overvaluation of internet stocks.

Why Is It Flashing Red?

According to MacroMicro, which uses gross domestic product (GDP) rather than GNP, the Buffett Indicator is currently at around 234 percent. LongTermTrends places it at 237 percent as of Friday, though both are at or close to record highs and have for over a year exceeded Buffett’s “playing with fire” threshold.

This means U.S. equities are valued at more than double the country’s economic output, one of many signs observers cite when discussing market overvaluations and the possibility of an AI “bubble” forming and preparing to burst.

Last year, David Rosenberg, founder of the economic and market insights firm Rosenberg Research, told Newsweek that the Buffett Indicator was one of “myriad” metrics pointing to overvaluation within equity markets.

According to calculations from the Motley Fool, around a third of the U.S. stock market—and by extension a large share of the money tied to 401(k)s and Americans’ retirement funds—is represented by the “Magnificent Seven” companies: Alphabet, Amazon, Apple, Meta, Microsoft, Nvidia, Tesla. Almost all are major investors in AI, and this has driven much of their market performance in recent years.

Beyond this extreme concentration, the combined valuation of AI-linked firms has increased by $27 trillion since late 2022, per Goldman Sachs, about one-third of the entire stock market’s value.

This has led to fears that valuations are rising far faster than revenue can justify, and that investor enthusiasm will give way to panic if AI investments fail to pay off. 2025 calculations from management consulting firm Bain & Company show the AI industry would need $2 trillion in annual revenue by the end of the decade to afford all the new data centers and compute that has been promised.

Reflecting his concerns over current investor enthusiasm, Buffett told CNBC in May that “we’ve never had people in a more gambling mood than now.”

“That doesn’t mean that investing is terrible,” he said. “It does mean that prices for an awful lot of things will look very silly.”

Contact Newsweek editors on this story: Matthew Cannon and Sam Wilson.