How do investors project their real rate of return over long horizons when doing valuations?

Hi all,

I’m learning more about stock valuation and have learned about the difference between nominal returns and real returns. This got me wondering - how exactly do investors project their real rates of returns for investments over long horizons - 20 years, 30 years, etc.? It’s easy to calculate real returns when looking into the past, but what formulas or strategies are used to predict real returns in the future?

Curious to know if there are any good videos or resources which can help me learn more about how to do those calculations.