7-9% is a range conservative estimate of the stock market returns since 1920; that is adjusting for inflation.

Here's one source that supports the 7-9% range over the last 30 years: https://www.sofi.com/learn/content/average-stock-market-retu....

1920 to 2022: 7.38% (adjusted for inflation) https://www.officialdata.org/us/stocks/s-p-500/1920?amount=1...

1989 to 2022: 7.4% (adjusted for inflation) https://www.officialdata.org/us/stocks/s-p-500/1989?amount=1...