Warren Buffett's Berkshire Hathaway Is Sounding a Warning. What History Tells Us.

Warren Buffett's Berkshire Hathaway (NYSE: BRKA)(NYSE: BRKB) is sitting on a record cash pile approaching $400 billion and has been a net seller of stocks for more than three years. At the same time, the famous "Buffett indicator" -- which compares the U.S. stock market to U.S. GDP -- has climbed to an all-time high.

A quarter of a century ago, Buffett called the Buffett indicator the "best single measure of where valuations stand." It recently topped 230%, meaning stocks are worth more than twice the nation's annual output. For perspective, that is far above the roughly 140% reading at the peak of the dot-com bubble in 2000. Add Berkshire's mountain of cash and its steady selling, and the message is hard to miss: Stocks look expensive.

Can history give us any guidance on how to react to these yellow flags?

What history says

Berkshire has built up cash before, and the timing has often been prescient. It held large cash reserves before the dot-com crash and again before the 2008 financial crisis, and in both cases, the caution proved wise. Investors who dismissed the defensiveness of Buffett & Co. in those moments learned a painful lesson. History suggests that when Buffett and his Berkshire pull back, it pays to take notice.

Warren Buffett. Image source: The Motley Fool.

But history also carries a second, humbling lesson. Markets can stay "overvalued" for years, climbing well past the point skeptics think possible.

Personal opinion here -- I think the AI market has been overvalued for too long. Also, the Buffett indicator has real flaws because it ignores low interest rates, the global revenue of U.S. companies, and the effect of stock buybacks, all of which can justify higher valuations than in the past. And Buffett himself has spent a lifetime warning against trying to time the market. He has stayed heavily invested through every scary headline, and those who sold everything on past "overvalued" signals often missed out on enormous gains while waiting for a crash that took years to arrive.

The takeaway for investors

So what should you do, given Berkshire's cash hoard, its stock sales, and the high Buffett indicator? Do not panic, and do not flee stocks entirely. The honest lesson is to do what Buffett's Berkshire does. It is not dumping everything; it is staying disciplined, refusing to overpay, holding good businesses, and keeping cash ready to pounce when fear returns. That is a template worth copying.

History tells us a Buffett indicator warning is rarely a signal to run for the exits. It is a reminder to prepare, to prioritize quality, and to keep some powder dry so that when the next downturn comes, you are the buyer rather than the seller.

Micah Zimmerman has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Berkshire Hathaway. The Motley Fool has a disclosure policy.