Focus on what's under the index

The S&P 500 can climb while most of its stocks go nowhere. A handful of giants carry the index, the headline looks healthy, and underneath the average stock is lagging. Traders call this narrow breadth.

Breakouts live underneath the index. A stock breaking out of a tight base needs fresh buyers to follow through, and in a narrow market the money is crowded into the same few names. We wanted to know if two simple breadth gauges could tell us when breakouts are likely to fail.

We tested both on every breakout from 2008 to 2026, as skip rules first, and then on top of our stock score. Here is what showed up in the data.