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- Arm stock made its trading debut on Thursday following its IPO that valued the company at $54.5 billion.
- It's the biggest US IPO since 2021, during a pandemic boom that saw massive valuations.
- The shares jumped 21% to $61.66 shortly after trading began around midday.
Shares of Arm made their much-anticipated trading debut on Thursday, marking the biggest US initial public offering of the year, and largest since 2021.