The indicator has climbed to a record high, Business Insider reported.
This signalled that stocks are overvalued and that another crash could be coming, it said.
The so-called Buffett indicator takes the combined market capitalisations of a country’s publicly traded stocks and divides it by quarterly gross domestic product.
Investors use it to gauge whether the stock market is overvalued or undervalued relative to the size of the economy.
Buffett, called the Oracle of Omaha, is a billionaire investor and the boss of Berkshire Hathaway.
He described the indicator in a Fortune magazine article in December 2001 as “probably the best single measure of where valuations stand at any given moment.”
The indicator has its flaws, including GDP not counting income earned overseas and US-listed companies not necessarily contributing to the US economy.
But it has a strong track record of predicting downturns — for example, it surged to 118% just before the dot-com bubble burst in 2000, and it topped 100% before the 2008 financial crisis.
“Nearly two years ago the ratio rose to an unprecedented level,” Buffett said in the Fortune article.
“That should have been a very strong warning signal.”
BUSINESS INSIDER