Stats › Concentration and breadth › Market breadth

Market breadth and equal weight

Concentration/breadth · 2023 to 1H 2026 · 2 sources · data as of 31 Jul 2026

When somebody says the market was up this year, they mean the index was up. That is not the same as saying most shares were up, and in some years it isn't even close. Breadth is the measure that tells you the difference, and the simplest version is just this: what share of the companies in the index actually beat the index.

This page has that number for the last few years, plus the cleanest test of the same idea, which is the equal weighted version of the S&P 500 against the ordinary cap weighted one. Same five hundred companies, same period, different weighting. The gap between them tells you how much of the market's move came from its largest members. I put it together because three years running, the headline S&P 500 return described a small minority of its own constituents, and almost nobody reporting the number mentioned it. That has consequences that go well beyond trivia. It changes how hard stock picking was, how you should read a fund manager's record, and whether the index return has anything at all to do with what you personally held.

Two sources, both from the same research shop, both linked underneath with their dates. That's a limitation and I'd rather say it up front than bury it. Check them against another provider if these numbers matter to you.