ARM has had a remarkable seven days — up 38% to $333.20 — and the most telling detail is that short sellers are not fighting it.
Short interest has drifted lower all month. The shares short number fell roughly 10% between early September and now, dropping from around 18.1 million to 16.4 million. That unwind accelerated precisely as the stock broke higher, suggesting bears covered into strength rather than adding. The ORTEX short score has also eased, sliding from 56.9 on September 9 to 52.4 by September 22 — a meaningful moderation that confirms the short community has turned less combative.
The lending market reinforces that picture of retreating pressure. Availability has opened up dramatically — from roughly 371% in early September to 719% now, meaning the pool of shares available to borrow has more than doubled relative to short interest. Cost to borrow ticked up about 10% on the week to 0.51%, but in absolute terms that remains trivially low. This is not a squeeze in any conventional sense; it is a rally that shorts chose not to contest. Options positioning adds nuance: the put/call ratio has actually dropped to 1.10, about 1.7 standard deviations below its 20-day average of 1.15. In a stock that has habitually run a structurally elevated PCR — the 52-week high is 1.35 — that shift toward calls is notable. After weeks of defensive hedging, some participants are now leaning into the upside.
The Street was caught offside. The last cluster of analyst actions, all from late July, mostly saw targets trimmed. UBS kept its Buy but cut from $360 to $320. TD Cowen stayed Buy but dropped from $475 to $350. Morgan Stanley held Equal-Weight and nudged its target to $212 — a figure now more than $120 below the current price. With ARM trading at $333, a meaningful chunk of the Street's published targets are now underwater. The consensus remains Buy (21 buys, 12 holds, 2 sells), but the target-price math looks increasingly stale heading into November 4 earnings. On valuation, the stock now trades at roughly 118x trailing earnings and 27x book — multiples that have expanded sharply, with the P/E up more than 31 points over both the past week and the past month. The bull case hinges on Armv9 royalty ramp and a potential $15 billion CPU revenue opportunity by fiscal 2031. The bear case points to SoftBank's 86% ownership concentration and the risk that existing customers balk at higher royalty rates.
Institutional ownership data underscores just how SoftBank-dominated the float truly is. SoftBank holds 86.4% of shares. The entire remaining institutional universe — Invesco, Capital Research, Arrowstreet, Fidelity and others — collectively accounts for a few percentage points. That thinness of the freely traded float helps explain the violence of the weekly move: a relatively small number of shares chased by a suddenly bullish market. Capital Research added 3.5 million shares as recently as August, and Arrowstreet added 3.1 million in June — both meaningful additions on a percentage-of-float basis given how little is actually tradeable. On the insider side, the only open-market activity of note from the past 90 days is CFO Jason Child's 10,400-share sale in August under a pre-arranged 10b5-1 plan — a scheduled transaction rather than a discretionary signal.
Peer performance confirms this was a broad semiconductor re-rating, not an ARM-specific event. AMD gained 24% on the week, MRVL rose 18%, and CEVA added nearly 20%. ARM's 38% move outpaced all of them, which likely reflects a combination of its AI-architecture premium and the thin float dynamic. Earnings on November 4 will determine whether the royalty ramp narrative can justify a stock price that has now lapped most analyst targets set just eight weeks ago.
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