Another thing to look at is the CAPE ratio. Even now, it's still above 30. We've gone from around a 37 to a 32. Mean/median is in the 16-17 range. DotCom crash in 1999 topped out at around 44.
The historic average for interest rates is considerably higher than it is right now.
Considering the amount of public debt outstanding - it's extremely unlikely we're returning to those levels of interest rates long-term (short-term I suppose anything can happen).
Interest rates have a huge effect on P/E. I wouldn't expect CAPE to match historic trends if interest rates don't.
US government can’t afford 4%. Rates will rise until something breaks, but 4% will be transitory if it gets there at all. My bet is things break sooner than that.
Still a lot of room to fall.