The value of the index tells very little. You must compare market cap to something and look at the ratio.
Here is good summary of important ratios December 27, 2019 https://www.yardeni.com/pub/valcapsales.pdf SP500 price to sales, price to earnings, market capitalization, TOBIN’S q.
We don't know what happens, but it's certain that if you buy SP500 at current price level, you must accept significantly smaller return next 10 years than previous 10 years.
Here is good summary of important ratios December 27, 2019 https://www.yardeni.com/pub/valcapsales.pdf SP500 price to sales, price to earnings, market capitalization, TOBIN’S q.
We don't know what happens, but it's certain that if you buy SP500 at current price level, you must accept significantly smaller return next 10 years than previous 10 years.