I'm not sure I agree the S&P's growth rate dropped suddenly post-1999. There was a serious market downturn from 2000-2008, but that's just a normal part of market action over the long term.

I sometimes like to look at what the underlying business are doing, rather than varying the start and end period to mitigate the effect of sentiment. Instead, we can just cut out sentiment completely.

One approach is to look at the sales per share - economically meaningless to investors on its own but fairly good when comparing a broad basket of businesses over different periods, as it doesn't suffer the fluctuations that earnings do.

From 2000-2023 sales per share of the S&P500 went from 780 to 1714, not adjusting for inflation. That is 3.6% per year. Adjusting for inflation of around 3%, sales per share have almost not increased at all since 2000, even after all the buybacks. Not much growth - in fact, none. For each dollar invested today, we are getting only about the same real sales that we got when investing even in 2000. You'd think that waiting 23 years is a long time for such little improvement in business.

Real annual sales per share growth of the S&P500 was higher looking back 100 years, in the 1% to 2% range. Business has slowed down a little the last 23 years.

Corporate margins did increase but that has happened in the past, and they can revert backwards also as business policy changes. (Corporate earnings to GDP is a similar concept to margins, given that GDP means sales. You can see that margins were high also in the past, and declined, and can do again.)
economist.com - Media assets

Over the next 23 at least mentally be prepared for - even if you don't believe this to be the case - more headwinds for business owning to relatively higher resource constraints and necessary regulations for environmental effects.

- Manlobbi