United Microelectronics Corporation has just put in one of the more striking price moves in the Taiwanese foundry space — up 75% over the past month, 15% in a single week — and borrowing costs are rising sharply in response, compressing the short side's room to manoeuvre.
The cost-to-borrow story is the most notable development in the lending market this week. CTB has roughly doubled in a month, reaching 3.38% by May 26 from around 1.83% a month ago — a move that accelerates into a steeper curve over the past five sessions alone. That said, this remains a moderate rate by global standards; shorts are paying more, but they're not being squeezed out. Availability is tightening too, dropping from around 134–140% in mid-May to just under 109% now. Availability is still in a range where fresh borrows are accessible — well above the 52-week low of 19% — but the direction is unambiguous. The lending market is becoming less hospitable as the stock climbs.
Short interest itself is a secondary angle here rather than the headline. At roughly 3.3% of the free float, the SI level is meaningful but not extreme. What's notable is that it has been essentially stable over the past month — shorts have not rushed to cover despite the enormous price move, and they have not materially added either. The combination of a 75% price rally and a flat short base implies significant mark-to-market pressure on existing positions, even if the aggregate count hasn't shifted dramatically.
The Street remains cautious, which adds an interesting tension to the tape. The analyst consensus on 2303 is a hold, with 11 hold ratings and 3 underperform calls — no buy ratings visible in the current data. At the same time, the stock has re-rated sharply: the price-to-earnings multiple is now at 27.2x, up nearly 10 points over 30 days, and price-to-book has expanded from roughly 2.3x to 4.0x in the same period. The analyst recommendation divergence score ranks in the 98th percentile — a signal that the current consensus is sitting well below where the price is trading, a gap that will draw attention when the next round of target revisions arrives. EPS surprise scores rank in the 84th percentile, and EPS momentum over 30 days ranks 77th — fundamentals are holding up the narrative for now.
The institutional footprint gives a useful read on who holds the base. BlackRock added more than 132 million shares in the most recent reporting period, lifting its stake to 7.6% — the single largest disclosed move among top holders. UBS Asset Management also added about 18 million shares, bringing its position to roughly 0.77% of shares outstanding. Most other large holders — Cathay, Yuanta, Fuh Hwa — were unchanged in the latest filings, suggesting the recent move has been driven by active international buyers rather than a domestic reshuffling.
Peer performance on the week offers some context for the breadth of the move. 2302 — a closely correlated name — was up 36% on the week and nearly 10% in a single session. 5285 added 18% over five days. The rally in 2303 is therefore not an isolated re-rating; it reflects a broader wave through Taiwanese semiconductor names. The prior earnings print on April 29 produced a 2.9% next-day gain and a 22% five-day move, so the stock has form for sharp reactions. The next earnings event is scheduled for July 29.
With CTB still rising, availability tightening, and the consensus hold rating now sitting against a P/E near 27x, the July print becomes a clear focal point — both for shorts managing an uncomfortable position and for analysts deciding whether to revise targets that look increasingly stale against where the stock is trading.
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