In March 2020 they were down 30% from the peak a month before. There was a virus. You may have heard about it? It was in the news. :) People didn't know what was going to happen.

Previous peak to present might be a less misleading factoid. And that is +20%. Still a big number but less impressive. It may be that confidence in public markets was bolstered by the resilience of the big companies' profits in the face of the virus.

+23% peak to peak actually.

Ok you want a longer period? it’s up nearly 70% from start of 2019, and it’s PE ratio is among the highest in its history.

You picked another trough as your baseline. Only up ~40% since Oct 2018. Still two very big years -- double the long run historical average -- but also a good deal less sensational than the numbers you're pulling out.

For what it's worth, a look at the annualized returns chart for the S&P500 might be interesting. https://www.macrotrends.net/2526/sp-500-historical-annual-re... Those green bars on the right don't look tremendously out of place compared to past years. What's really different from previous decades is not the rate of growth but the lack of financial market downturns. Hard to say if that means we're ramping up to "the big one" or if we have fundamentally figured out how to better run the economy so that we have fewer downturns.

Record low interest rates have a lot to do with it. If they rise significantly that 38 PE will get slashed a great deal.

Right, the question is whether the record low interest rates will actually need to be slashed at all. We are seeing some inflation in some sectors -- lumber, computer hardware, probably other things I'm not mentioning. But it's not clear whether this inflation is from supply shocks, displaced consumption due to COVID, or monetary issues. I mean, it's all three, but it's not clear how much of the responsibility lies with each cause.