Nasdaq-100 Index Reconstitution Adds Six New Companies, Removes Six Others Effective Dec. 22

Nasdaq said the annual reconstitution of the Nasdaq-100 will take effect prior to market open on Dec. 22, 2025, with six additions—Alnylam Pharmaceuticals (ALNY), Ferrovial SE (FER), Insmed (INSM), Monolithic Power Systems (MPWR), Seagate Technology (STX) and Western Digital (WDC)—and six deletions—Biogen (BIIB), CDW (CDW), GlobalFoundries (GFS), Lululemon (LULU), ON Semiconductor (ON) and The Trade Desk (TTD), thereby altering the index’s composition ahead of the year‑end rebalance.

Analysis

Nasdaq announced the annual reconstitution of the Nasdaq-100 Index will take effect prior to market open on December 22, 2025, adding six companies—Alnylam Pharmaceuticals (ALNY), Ferrovial SE (FER), Insmed (INSM), Monolithic Power Systems (MPWR), Seagate Technology (STX) and Western Digital (WDC)—and removing six companies—Biogen (BIIB), CDW (CDW), GlobalFoundries (GFS), Lululemon (LULU), ON Semiconductor (ON) and The Trade Desk (TTD). The change preserves the index size but materially alters its constituent list ahead of year‑end rebalancing.

Signals show a neutral headline sentiment but a market_impact_score of 0.3, indicating modest technical flows; per-ticker sentiment is positive (0.5) for additions and negative (-0.5) for deletions, implying expected passive inflows into the added names and outflows from the removed names around the reconstitution. This suggests short-term demand/supply imbalance rather than company-specific fundamental news.

Thematic outputs highlight Market Technicals & Flows, Technology & Innovation, and Healthcare & Biotech, indicating the reconstitution shifts sector exposure within the index. Investors should treat price moves as likely technical and transient, monitor ETF and index-tracking fund activity and liquidity around Dec. 22, and avoid assuming inclusion reflects a near-term change in company fundamentals.

Key Decisions for Investors

• Monitor ETF and index-tracking fund flows and intraday liquidity for ALNY, FER, INSM, MPWR, STX and WDC ahead of and immediately after Dec. 22, 2025, because the market_impact_score of 0.3 implies modest technical pressure that can create short-term volatility
• If underweight the additions, consider tactical exposure but size positions conservatively and preferably wait for price normalization post-reconstitution since the moves are driven by technical flows rather than new fundamentals
• Reduce exposure to or hedge holdings in the names being removed (BIIB, CDW, GFS, LULU, ON, TTD) where appropriate and reassess portfolio sector exposures to reflect the index composition change