FTSE Russell, which manages one of the most widely tracked stock indexes, is switching from one annual rebalance to two per year. The first extra rebalance will happen in Q4 2026, according to a November 2025 index notice. The change was confirmed on the FTSE Russell website as of June 23, 2026.

Under the new schedule, rebalances will happen on two fixed dates: the fourth Friday in June and the second Friday in December. June is the existing annual event. December is the new one. To give you a sense of scale: in 2024, the June rebalance happened after markets closed on Friday, June 28, and took effect the following Monday when trading opened.

What's Actually Changing

The communication timeline for the June rebalance is already set. Preliminary lists of which stocks will be added or removed come out May 22, with updates on May 29 and June 5. FTSE Russell hasn't yet published the full schedule for the December cycle, so portfolio managers tracking Russell benchmarks should check the index provider's notices as the date approaches. The December rebalance has been labeled for Q4 2026, which technically means anywhere from October through December—though "second Friday in December" would point to December 11, 2026, if that rule applies from the start.

Why This Matters to Investors

If you own a passive fund, ETF, or any investment that tracks the Russell 1000, 2000, or 3000 index, you now have two forced trading days a year instead of one. On rebalance dates, fund managers sell stocks being removed and buy stocks being added—all at roughly the same time. The June rebalance already creates some of the biggest single-day trading surges in US markets. Adding a December rebalance will create a second one in a month that already sees thinner trading around the holidays, year-end tax-loss harvesting by individuals, and window-dressing by money managers trying to make their holdings look better on year-end statements. How all these pressures collide with the mechanical buying and selling that rebalances require is hard to predict.

For stocks on the edge of Russell index eligibility, the timing change compresses how long they can trade at unusual prices. Suppose a mid-cap stock used to jump in market value in August. Under the old annual schedule, it would wait roughly ten months for the next rebalance opportunity. Now it would wait at most five months. That means fewer months during which the stock can trade at the price premium or discount that investors bet on before reconstitution day.

Active money managers—those who pick stocks rather than blindly track an index—face a different challenge. Between rebalances, a Russell index drifts as some stocks rise and others fall. That drift used to reset once a year. Now it resets twice. Fund managers who try to track Russell indexes closely will need to adjust their computer models that measure and manage how much their holdings differ from the benchmark. This gets trickier because many institutional investors measure performance from January through December, and a December rebalance lands right on year-end, creating extra noise in annual results.

The trend toward more frequent rebalancing across the index industry reflects pressure from fund managers who want their indexes to move less and trade better. Larger batches of buying and selling on a single date can drive prices up or down—a cost that shows up in fund returns. Splitting that demand across two dates might shrink any one shock, though whether it cuts total market impact or just spreads it out differently is a question the market will answer with real data now.

Until FTSE Russell publishes the formal schedule for December rebalances, treat the December 11, 2026, date as a working estimate. Practitioners should monitor the index provider's notice feed as the date approaches.