Russell Index Now Rebalances Twice Yearly, Adding December Turmoil

FTSE Russell moves its US index reconstitution to a semi-annual schedule starting Q4 2026, adding a second annual rebalance in December alongside the existing June event. The June reconstitution already generates massive single-session volume. December's addition hits during thin holiday participation, year-end tax-loss harvesting, and window-dressing—a forced-turnover event stacked atop seasonal pressures. Index-tracking funds will face coordinated portfolio shifts twice yearly.