Are You Actually Diversified? What Owning the S&P 500 Really Looks Like Right Now

If you own a target date fund in your 401k or an S&P 500 index fund in a brokerage account, you probably feel pretty diversified. You own 500 companies. That's the entire point of indexing.

But the S&P 500 of 2026 is not the S&P 500 most investors picture in their heads. A handful of names are doing most of the work, and the gap between what people think they own and what they actually own has rarely been wider.

Here is what is going on, why it matters, and how to think about your own portfolio in light of it.