What Top-10 Concentration in a 13F Really Tells You

The definition

Top-10 concentration is the share of a filing's total reported value held in its ten largest positions. It is the fastest single-number summary of how much a manager distinguishes between ideas: an equal-ish 100-stock book scores under 20%, while a 6-stock book must score 100%. Our Portfolio Concentration ranking publishes it for every tracked fund, latest quarter.

The real distribution on this site (2026-Q2)

Across 95 funds with usable filings, the median top-10 weight is 36%, the 10th percentile is 21% and the 90th percentile is 91%. But the average hides the structure: concentration is a *style* variable, and style follows manager type.

At the extremes: Himalaya Capital, Dragoneer, Paulson and Linden Rose sit at 100% — every dollar of their US long book lives in ten names or fewer. At the other end, Two Sigma (8.8%), Royce (9.1%), Renaissance (12.0%) and AQR (12.2%) hold hundreds of positions where no single bet matters much.

Concentration changes are the signal, not the level

A static 97% concentration at Himalaya is just its style. The readable events are transitions: a diversified fund suddenly compressing into ten names, or a concentrated book suddenly spreading out. The first often marks a manager moving from research to conviction (watch whether the new top names are brand-new positions); the second often marks de-risking — which tends to happen when the manager sees the market as expensive, not when it is calm.