(Bloomberg) -- A 34%, three-day surge in SoftBank Group Corp. has pushed its shares to the most overbought level in more than two decades on the back of Arm Holdings Plc.’s explosive rally. 

The 14-day relative strength index for SoftBank hit 88 on Tuesday, exceeding the level of 70 that signals to some traders that an asset’s gains may have been excessive. The RSI is the highest since July 9, 2003, a date that was followed by a two-day plunge of more than 20% in the stock’s price. 

SoftBank Group owns about 90% of Arm, which has almost doubled in value since the chip designer made the case last week for how it will benefit from an artificial intelligence boom.

Read: SoftBank Shares Climb Again With Arm’s Explosive AI Rally

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