Index Rebalancing Overview

S&P Dow Jones Indices announced a series of benchmark rebalancings on Thursday, 2 Oct 2026, with the changes taking effect prior to the market open on Tuesday, 6 Oct. The reshuffle reflects ongoing corporate M&A activity and capital‑structure transformations across multiple sectors.

Twilio Inclusion Details

Twilio Inc. Class A (NYSE:TWLO) will be elevated from the S&P MidCap 400 to the flagship S&P 500, effective 6 Oct 2026. Twilio replaces Warner Bros Discovery Inc (NASDAQ:WBD), which is in the final stages of an acquisition by Paramount Skydance Corp (NASDAQ:PSKY). Following the announcement, Twilio shares rose 1.6 % in extended trading as index‑tracking funds anticipated the inclusion.

Related Component Movements

  • FormFactor Inc (NASDAQ:FORM) will fill Twilio’s vacated slot in the S&P MidCap 400, moving up from the S&P SmallCap 600.
  • The S&P SmallCap 600 will in turn absorb Workiva Inc (NYSE:WK), which replaces FormFactor; Workiva shares gained 2.7 % after‑hours on the news.
  • Newly formed Consumer Staples entity Vylor Inc joined the S&P 500 on Thursday after spinning off from Corteva Inc (NYSE:CTVA).
  • Post‑spinoff, Corteva will transition to the S&P MidCap 400 on 6 Oct to align with its revised market‑capitalization profile.
  • Corteva’s move displaces Olin Corporation (NYSE:OLN), which shifts to the S&P SmallCap 600, taking the place of chipmaker Qorvo Inc (NASDAQ:QRVO).
  • Qorvo is being acquired by Skyworks Solutions Inc (NASDAQ:SWKS), a pending transaction that triggered the chain of small‑cap reallocations.

Market Reaction

Beyond Twilio’s 1.6 % after‑hours gain, Workiva posted a 2.7 % rise, while other affected equities recorded muted price reactions. Index component tickers showed modest moves: US500 +0.20 %, WBD ‑0.02 %, PSKY ‑9.58 %, FORM ‑0.58 %, OLN +2.97 %, MID ‑0.62 %, SWKS ‑2.73 %, SP600 ‑0.67 %, WK +4.60 %, QRVO ‑1.98 %, TWLO +3.01 %, CTVA ‑83.81 %.

Compliance and Timing

All changes are scheduled to be effective before the market opens on Tuesday, 6 Oct 2026, and are subject to the standard S&P Dow Jones index methodology governing eligibility, market‑cap thresholds, and liquidity criteria.