The Buffett Indicator is the ratio of total the United States stock market valuation to GDP. It is said to be the best predictor of market corrections or crashes.
As of May 6, 2021:
Historically, when the stock market went above GDP by 50-100% it crashed, going below GDP. 2021 is the year in the last 100 years when the ratio was over 2x the largest stock market in history.
In 2021, Elon Musk asked Cathie Wood, the famous tech-focused investor from Ark investments, what is her explanation for the high Buffet indicator (a ratio of US stock market/GDP). Cathie suggests a few reasons: