I’ve seen 8% in some places and 10% in other places. Investopedia has 10%. https://www.investopedia.com/ask/answers/042415/what-average-annual-return-sp-500.asp#:~:text=The%20S%26P%20500%20index%20is,since%20its%20inception%20through%202019.

The 10% includes stock price appreciation. For the most part I’d stay away from any stock yielding an 8% dividend because it’s more than likely too good to be true (i.e. unsustainable).