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Equal weight against cap weight

Concentration/index construction · 2000 to 2026 · 3 sources · data as of 31 Jul 2026

Take the S&P 500 and hold every company in it in exactly the same amount. The same money in the smallest as in the largest. That's the equal weighted version of the index. Identical companies to the one everybody quotes, in completely different proportions, rebalanced back to level every quarter.

This page puts the two side by side. What the difference was worth across the 2000s, how the relationship flipped in the years after, and where the two stand in the first half of 2026. The reason it gets a page of its own is that it isolates one single variable. No stock picking, no timing, no sector calls. Same five hundred names, different position sizes, and outcomes that diverge by an amount most people would not believe if you told them. There's a section further down on when each construction wins, which has a fairly obvious logic once you see it, and a section on the costs of the equal weighted version, which almost nobody mentions when they show you the headline gap.

Three sources sit behind this, all dated and linked at the bottom. The 2000s figures and the 2026 figures come from different places, so they aren't one continuous series, and I'd rather you know that going in than find it out later.