Western Digital Corp. (NASDAQ:WDC) shares rose 1.7% on Monday after the company was named as one of the new constituents of the Nasdaq-100 Index following its annual rebalancing.
The data storage group is among six companies added to the widely followed benchmark, which measures the performance of the 100 largest non-financial stocks listed on the Nasdaq. Other newcomers include Seagate Technology Holdings (NASDAQ:STX), whose shares gained 2%, Alnylam Pharmaceuticals (NASDAQ:ALNY), up 0.9%, Ferrovial SE (NASDAQ:FER), which advanced 0.7%, Insmed (NASDAQ:INSM), rising 1.2%, and Monolithic Power Systems (NASDAQ:MPWR), up 1.3%.
Nasdaq said the updated index composition will become effective before the opening bell on Monday, December 22, 2025. The Nasdaq-100 is reviewed each December, with the changes taking place alongside the quarter’s quadruple witching expiration.
As part of the reshuffle, six companies will exit the index: Biogen (NASDAQ:BIIB), CDW Corporation (NASDAQ:CDW), GlobalFoundries (NASDAQ:GFS), lululemon athletica (NASDAQ:LULU), ON Semiconductor (NASDAQ:ON), and The Trade Desk (NASDAQ:TTD). Shares of lululemon slipped 1.1% following the announcement.
The Nasdaq-100 is closely tracked by investors worldwide, with more than 200 investment products linked to the index and over $600 billion in assets under management. The best-known of these is the Invesco QQQ Trust (NASDAQ:QQQ), which seeks to mirror the index’s performance before fees.