A ranking rather than a selection. Where the S&P 500 has a committee deciding what belongs, the Russell family simply counts down from the top — and the difference shows.
The Russell US indexes nest inside one another. The Russell 3000 holds roughly the 3,000 largest US companies. The Russell 1000 is its largest thousand. The Russell 2000 is everything else in the 3000. Together the two smaller indexes reconstitute the larger one exactly.
This is the interesting contrast with the S&P 500, and the reason both families coexist.
The S&P 500 applies eligibility criteria — including a profitability test — and then a committee decides. Size alone does not qualify a company, and a large, well-known business can wait years for admission.
The Russell indexes rank and cut. If a company is large enough on the ranking date and meets basic eligibility, it is in. There is no earnings screen and no discretion about whether it deserves inclusion. The index provider's stated position is that an index should represent the entire investable opportunity set rather than a curated version of it.
Both positions are defensible. A mechanical rule cannot avoid absurdities; a committee introduces judgment that cannot be audited from outside. What matters is knowing which one you are holding.
The Russell 3000 is the closest thing to a census of investable US equity, and its aggregate value tracks the market's overall expansion. At the April 2026 ranking date its total market capitalization stood at $75.6 trillion, up 29% from $58.4 trillion a year earlier.
Within that, concentration at the top continued. The seven largest technology and platform companies grew 49% over the same period to a combined $22.4 trillion — a figure that puts the concentration discussion on the S&P 500 page into context, since those same companies dominate both.
Membership across the whole family is rebuilt on the same schedule. From 2026 that schedule is semi-annual: the full June rebuild plus a size-focused December event. At the June 2026 reconstitution, preliminary lists indicated 62 companies joining the Russell 1000 — most of them moving up from the small-cap index.
The mechanics and market impact are covered in detail on the Russell 2000 page, where the effect is largest.
Both cover US large caps and correlate closely. The Russell 1000 is broader and rules-based; the S&P 500 is narrower, committee-selected and requires profitability.
As a proxy for the whole investable US equity market, typically by mandates that want total-market exposure rather than a size segment.
No. They are mutually exclusive and together make up the 3000 exactly.