Warren Buffett's $187 Billion Warning to Wall Street Echoes Louder Than Ever, Thanks to His Favorite Valuation Measure

This has shaped up to be another stellar year for the stock market, with the timeless Dow Jones Industrial Average (DJINDICES:^DJI), benchmark S&P 500 (SNPINDEX:^GSPC), and game-changing Nasdaq Composite (NASDAQINDEX:^IXIC) catapulting to new highs. But don't tell that to Berkshire Hathaway's (NYSE:BRKA)(NYSE:BRKB) newly retired CEO, Warren Buffett.

Although the Oracle of Omaha has repeatedly told investors that he'd never bet against America and is a devout supporter of long-term investing, he was a net seller of equities for 13 consecutive quarters, totaling approximately $187 billion, leading up to his Dec. 31 retirement as CEO.

Berkshire's now-former boss was a persistent net seller of equities leading up to his Dec. 31 retirement. Image source: The Motley Fool.

Actions speak louder than words, and Warren Buffett's persistent selling can be best explained by his favorite valuation measure.

The Oracle of Omaha has always been a stickler for value

In more than half a century at the helm of Berkshire Hathaway, Buffett broke several of his unwritten investing rules. He sometimes purchased stocks for short-term gain (e.g., buying Activision Blizzard for an arbitrage opportunity) and piled into heavily indebted companies, such as Occidental Petroleum (NYSE:OXY).

But the one "rule" Berkshire's billionaire boss refused to break had to do with value. If the Oracle of Omaha didn't believe he was getting a good deal, he wouldn't buy or hold shares of a public company.

Although Buffett rarely, if ever, discussed Berkshire's individual stock holdings, he did label his preferred valuation metric during a 2001 interview with Fortune magazine. Buffett proclaimed the market-cap-to-GDP ratio, now affably known as the Buffett indicator, to be "probably the best single measure of where valuations stand at any given moment."

Stock Market reaches most expensive valuation in history after the Warren Buffett Indicator hits 239%, surpassing the Dot Com Bubble, the Global Financial Crisis, and the 2022 Bear Market 🤯 👀 pic.twitter.com/K5LBAN6S2Q

— Barchart (@Barchart) August 15, 2026

This ratio, which divides the cumulative value of U.S. public companies by U.S. gross domestic product (GDP), has averaged roughly 89% since December 1970. In other words, the aggregate value of public companies has averaged 89% of U.S. GDP over 56 years.

On Aug. 12, the Buffett indicator blasted to an all-time high of 240.24%, or approximately 170% above its 56-year average. This means Buffett was a persistent net seller of stocks for 13 consecutive quarters because value has become increasingly difficult to find amid an artificial intelligence-driven stock market.

Image source: Getty Images.

Warren Buffett's warning also highlights long-term investors' opportunity

While Warren Buffett's $187 billion warning echoes louder than ever, even after his retirement, it also speaks to the presumed opportunity that lies ahead for optimistic, long-term-minded investors.

Throughout Buffett's time as Berkshire's boss, he frequently chose to sit on his hands and build up his company's treasure chest when stock valuations weren't palatable. Though Berkshire's shareholders preferred to see Buffett put his company's capital to work, patience often paid off handsomely.

Berkshire Hathaway's massive cash pile declined for the first time in 4 years, meaning it was finally a net buyer of stocks 🤯 👀 pic.twitter.com/s1AJeQxlO9

— Barchart (@Barchart) August 9, 2026

For example, Warren Buffett's patience translated into tens of billions of dollars in gains, courtesy of Bank of America (NYSE:BAC). In August 2011, Berkshire's chief gave Bank of America $5 billion to bolster its balance sheet after the financial crisis and received $5 billion in BofA preferred stock, yielding 6%, in return.

However, the real treasure was the 700 million stock warrants Berkshire received that could be exercised at $7.14 per share. Buffett exercised these warrants in mid-2017 for a windfall profit.

Patience isn't always sexy on Wall Street, but maintaining perspective and playing the long game worked well for Berkshire's boss, and should continue to do so for his successor, Greg Abel.

Bank of America is an advertising partner of Motley Fool Money. Sean Williams has positions in Bank of America. The Motley Fool has positions in and recommends Berkshire Hathaway. The Motley Fool recommends Occidental Petroleum. The Motley Fool has a disclosure policy.