The very high and very speculative participation by retail investors is scaring me. I'm reminded of the story of the hedge fund manager who was getting a shoe shine, and the shoe shine boy was giving him stock tips. He closed out his positions and correctly called the top of the bubble[1]. I don't know if the story is true, and it is just an anecdote anyway. But historically this kind of activity does mark the end of bull markets.

At the same time I keep hearing that the stock market is actually undervalued on average given current interest rates - and those aren't going to change anytime soon.

Definitely things are frothy and there are bubbles in some stocks, but maybe this market still has legs - at least while the fed is buying 120 billion of debt each month.

[1] I found it, it was Joe Kennedy in 1929: https://archive.fortune.com/magazines/fortune/fortune_archiv...