A wise professor once told me "once the last stalwart hold out has bought into the market the end is near". Once you're to the point where everyone is seemingly in the market and people that shouldn't be are in, too, you're probably in for a swing downward. The Feds aversion to raising rates is really telling.

You don't have to wait until the bottom, but it's obviously better to buy assets when they are "cheap" rather than "expensive".

Valuation and long-term future returns seem indeed related historically https://www.oppenheimerfunds.com/private-client-groups/artic...

For a more detailed treatment: https://personal.vanguard.com/pdf/s338.pdf

Of course this kind of arguments are not bullet-proof, see for example: http://www.philosophicaleconomics.com/2014/06/critique/

And one could have missed the last years of bull market applying these arguments already in 2013 (it doesn't mean that the conclusion was wrong with the 2023 horizon, though).

Anyway, ignoring valuation completely doesn't seem the right thing to do and people try to forecast returns to make asset allocation decisions: https://www.researchaffiliates.com/en_us/asset-allocation.ht...

I wouldn't call that market timing.