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.

If you have been watching gas prices climb over the past few weeks, you are not alone. Conflict in the Middle East has disrupted shipping through the Strait of Hormuz, a narrow waterway between Iran and Oman that carries roughly one-fifth of the world's oil supply. That disruption is filtering through to prices at the pump, grocery store shelves, and investment portfolios. Understanding why oil prices react so sharply to these events, and how this situation differs from tariffs or sanctions, can help you make sense of what you are seeing in the headlines.