Insights from the November 2025 Russell US Indexes Parallel Run

This technical report details the findings from FTSE Russell's November 2025 parallel run, which was conducted to prepare for the transition from an annual to a semi-annual reconstitution frequency for the Russell US Indexes in 2026. The report outlines the importance of regular reconstitutions in accurately reflecting the evolving US equity markets, noting that the Russell Indexes have undergone multiple reconstitutions since their inception in 1984. The parallel run confirmed operational readiness and validated the methodology, demonstrating minimal impact on index characteristics. Key takeaways include the alignment of turnover and composition changes with expectations, indicating that the new semi-annual schedule will effectively reflect market developments while maintaining index integrity. The report also discusses the operational systems and controls that functioned smoothly during the test, establishing readiness for the new effective date in December 2026. Overall, the findings support the transition to a semi-annual reconstitution schedule without disrupting methodology integrity or index behavior.