By Rebecca Feng

Trade Desk (TTD): The advertising-technology company is poised to be the S&P 500's biggest loser this year. Its shares have slid by around two-thirds through Tuesday. The Californian company missed revenue estimates in February, and the stock was downgraded by analysts in August.

Western Digital $(WDC)$: The data-storage stock has surged nearly 300% this year, making it the S&P 500's winner. Hard-drive makers enjoyed a resurgence as investors bet on artificial intelligence's voracious need for digital storage. Shares of rival Seagate Technology $(STX)$ soared 225%.

Strategy (MSTR): The bitcoin-accumulation company was the biggest loser in the Nasdaq composite this year, even after it took steps in December to insulate itself from the cryptocurrency selloff. Shares dropped 46% through Tuesday.

Siemens Energy (XE:ENR): The German energy company claimed the top spot in the Euro Stoxx 50 index, rising 139% this year. The company's results beat expectations in January, and it boosted its long-term outlook in November.

Micron Technology $(MU)$: Chip makers were investor darlings, propelled by the U.S.-China AI arms race and an epic capital-spending boom. Micron jumped by nearly 250% through Tuesday. AMD $(AMD)$ and Nvidia (NVDA) were both set for hearty double-figure percentage gains.

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(END) Dow Jones Newswires

December 31, 2025 07:41 ET (12:41 GMT)

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