[rsynnott]

> I suppose I'm just a little worried about a 10 year sideways market.

In that case possibly go with something global; in the one recent period where S&P500 was pretty much sideways for 10 years, MSCI World, say, did somewhat better. If the wheels do fall off for the AI bubble, it'll probably hit the US market harder than others.

_Within reason_ (you probably don’t want an index that has literally every stock in the world, say), broader indexes are generally less volatile than narrower ones; must downturns are at least somewhat regional, and sectoral downturns hit some regions harder than others.