https://i.imgur.com/rKZX1vf.png

The picture above shows the Buffet Indicator. It is simply the ratio of publicly-traded U.S. stocks to U.S. GDP.

https://www.investopedia.com/news/buffett-indicator-spells-bad-news-stock-investors/

Mike Maloney did explain it in this video which is quite concerning.

https://www.youtube.com/watch?v=jB6iAWQPa2k