Western Digital stock rises after inclusion in Nasdaq-100 Index

Investing.com -- Western Digital Corp. (NASDAQ: WDC) stock rose 1.7% Monday following the announcement of its inclusion in the Nasdaq-100 Index as part of the annual reconstitution.

The data storage company was among six firms added to the influential index, which tracks the performance of the 100 largest non-financial companies listed on the Nasdaq Stock Market. Other additions included Seagate Technology Holdings (NASDAQ: STX), which gained 2%, Alnylam Pharmaceuticals (NASDAQ: ALNY), up 0.9%, Ferrovial SE (NASDAQ: FER), rising 0.7%, Insmed (NASDAQ: INSM), up 1.2%, and Monolithic Power Systems (NASDAQ: MPWR), which climbed 1.3%.

The changes will take effect prior to market open on Monday, December 22, 2025, according to Nasdaq's announcement. The reconstitution occurs annually in December, coinciding with the quadruple witch expiration Friday of the quarter.

Six companies will be removed from the index as part of the rebalancing: Biogen (NASDAQ: BIIB), CDW Corporation (NASDAQ: CDW), GlobalFoundries (NASDAQ: GFS), lululemon athletica (NASDAQ: LULU), ON Semiconductor (NASDAQ: ON), and The Trade Desk (NASDAQ: TTD). Lululemon shares fell 1.1% following the news.

The Nasdaq-100 Index is widely tracked by investors, with more than 200 products based on the index representing over $600 billion in assets under management globally. The most prominent of these is the Invesco QQQ Trust (NASDAQ: QQQ), which aims to track the index's performance before expenses.

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