By Noel Randewich
(Reuters) - Shares of Arm Holdings (NASDAQ:ARM) surged more than 40% on Monday, adding to a staggering rally fueled by optimism around artificial intelligence.
The stock last traded up 21% at $139.65 after reaching as high as $164, 42% above its close on Friday.
With Monday's jump, Arm's shares have gained more than 80% since the British tech company last Wednesday became Wall Street's newest AI-related darling following a quarterly outlook that beat Wall Street's expectations.
Arm's stock market value has now reached a record $141 billion, nearly tripling since its initial public offering last September.
About 10.5 million Arm shares, worth about $1.4 billion, have been sold short by traders betting the stock will fall, according to Ihor Dusaniwsky, managing director of predictive analytics atS3 Partners, which tracks short sellers.
However, there is little evidence Monday's stock surge is the result of a short squeeze, which occurs when short sellers rush to buy back shares in order to cover a potentially money-losing trade, Dusaniwsky said.
"Although there has been some short covering, the primary reason for the stock move is long share buying," Dusaniwsky said.
The recent spike in Arm's shares echoes sharp gains in Nvidia (NASDAQ:NVDA) in May 2023 after the Silicon Valley chipmaker said AI computing was fueling massive demand for its chips.
After Nvidia's stock market value more than tripled last year, on Monday it overtook Amazon.com (NASDAQ:AMZN) as the U.S. stock market's fourth most valuable company, just behind Alphabet (NASDAQ:GOOGL).
Unlike Nvidia, only a fraction of Arm's shares are available for trading. Following its IPO, owner Softbank (OTC:SFTBY) kept a 90.6% stake. The chip designer's 10 largest shareholders control almost 95% of its shares, according to LSEG data. That tiny supply of Arm shares available for trading may be contributing to the stock's recent surge.
By comparison, Nvidia's top 10 shareholders own about a third of the company.
Softbank could sell some of its Arm stake starting on March 12 after lock-up restrictions related to the IPO end.
With Monday's rally, Arm is trading at an exceedingly high 99 times expected earnings, even after analysts last week dramatically lifted their earnings estimates, according to LSEG data.
Nvidia's forward PE briefly hit 84 last June, but quickly fell as analysts raised their earnings estimates at a faster pace than the company's stock rally. Nvidia's stock is now valued at 34 times expected earnings.