Russell US Indexes Reconstitution

What the Russell reconstitution is

The Russell US indexes, including the Russell 3000, the large-cap Russell 1000 and the small-cap Russell 2000, are maintained by FTSE Russell, part of the London Stock Exchange Group (LSEG). Unlike the committee-run S&P 500, the Russell indexes are rebuilt by rule: companies are ranked by size, and fixed breakpoints decide which index each belongs to.

That rebuild is called the reconstitution. At each one, FTSE Russell re-ranks the eligible U.S. stock universe, adds and removes companies, moves companies between the Russell 1000 and Russell 2000, and updates the Growth and Value style indexes. Because a large amount of money tracks these indexes, particularly the Russell 2000, the reconstitution is one of the biggest trading events of the year for U.S. stocks.

From annual to semi-annual

For decades the Russell US indexes were reconstituted once a year, in June. FTSE Russell has said the indexes were reconstituted more often when they launched in 1984 and moved to an annual schedule in 1989.

FTSE Russell has now returned to a semi-annual schedule. The first December reconstitution under the new schedule takes place in December 2026, making June and December the two regular reconstitution months from then on. Details are set out in FTSE Russell’s announcement of the move to semi-annual reconstitution and in the schedules it publishes for each review.

How each reconstitution unfolds

Both reconstitutions follow the same sequence of steps, set out in a schedule FTSE Russell publishes ahead of time.

1. Rank day. Eligibility and market capitalisations are assessed as of the close on rank day. For June, rank day is the last business day of April. For December, it is the last business day of October.
2. Preliminary lists. FTSE Russell publishes preliminary lists of additions and deletions a few weeks later, after the U.S. market close, followed by updates as corporate events change the picture.
3. Query period and lockdown. Index users can raise questions about the lists, and in the final weeks before the effective date the lists enter a lockdown period.
4. Effective date. The changes take effect after the close on a Friday, and markets open the following Monday with the reconstituted indexes. In June this falls late in the month; in December, it falls after the close on the second Friday of December.

The exact dates for each review are published by FTSE Russell and are shown on this page when available.

How June and December differ

The two reviews are not identical.

• June is the full reconstitution. Size breakpoints are reset and the Growth and Value style indexes are fully reconstituted.
• December also re-ranks companies by size and resets the breakpoints between large, mid and small caps. But style changes are limited: new style assignments apply only to additions and to companies moving between the Russell 1000 and Russell 2000. Companies staying in the same index keep their June style assignments. FTSE Russell has said this avoids extra turnover from reassigning every stock’s style twice a year.

Separately, eligible initial public offerings are added to the indexes each quarter, in March, June, September and December, so newly listed companies do not have to wait for a reconstitution.

Why it can move stocks

Funds tracking the Russell indexes generally trade at or near the close on the effective date to match the new index composition. That creates heavy, concentrated buying in additions and selling in deletions, especially among small companies whose shares trade less actively. Closing-auction volume on reconstitution day is often among the largest of the year.

Common effects described in market commentary include price moves in stocks after the preliminary lists come out, as traders anticipate index demand, and occasional reversals after the effective date. These patterns are not dependable, and the move to two reconstitutions a year may change how they play out.

Common misreadings

• Assuming the Russell 2000 is the 2,000 smallest U.S. stocks. It is the smaller part of the Russell 3000, defined by rank and breakpoints, not the smallest listed companies overall.
• Thinking reconstitution happens only in June. It now happens in June and December.
• Confusing Russell with S&P. The S&P quarterly process is separate; see the S&P index rebalance.

Frequently asked questions

When is the Russell reconstitution?

Twice a year, in June and December. The June changes take effect after the close on a Friday late in the month; the December changes take effect after the close on the second Friday of December.

What is Russell rank day?

The date on which FTSE Russell measures eligibility and market capitalisation for the reconstitution: the last business day of April for June, and of October for December.

Has the Russell always been reconstituted once a year?

No. FTSE Russell says the indexes were reconstituted more than once a year after their 1984 launch, moved to an annual June schedule in 1989, and returned to two reconstitutions a year starting with December 2026.

Are IPOs added between reconstitutions?

Yes. Eligible IPOs are added quarterly, in March, June, September and December.

Explainer updated November 13, 2026.