I've done a bunch of work looking at yield spreads and forward long term returns ( this particular data set looks at forward 10-year returns ).

This is the latest reading that takes a modified Fed Model (using inverse CAPE ratio against the 10-year treasury yield) to estimate forward excess returns - which can be used as an implied equity risk premium (iERP). This data set is built using data from 1940 onward (I've also looked at 1900 and-on. The trend is still intact, just a little noisier - but I think that using the data post creation of the SEC and other regulatory bodies is more appropriate).

All signs point to stocks underperforming bonds through 2036 - this is obviously just a forecast, and there's a decent amount of scatter, but the trend seems pretty strong.

Some caveats.…