Taipei got off lightly, all things considered. The TAIEX fell 351.03 points, or 0.77%, to close at 45,511.49 on Tuesday, testing support at its quarterly moving average — a contained response to an ugly overnight lead. The Philadelphia Semiconductor Index had slumped 5.86% in Monday’s U.S. session after top executives from Anthropic, OpenAI, and xAI issued a joint call to slow the development pace of advanced frontier AI models, stoking fears of a deceleration in AI capital spending; Nvidia lost more than 3% and the S&P 500 eased 0.48%. Against that backdrop, a sub-1% decline in the world’s most semiconductor-heavy major index counts as resilience — though turnover contracted to the second-lowest daily level of 2026, so conviction on the buy side was thin.
The anchor was Taiwan Semiconductor Manufacturing Co. (2330), which added NT$5, or 0.21%, to NT$2,385 ahead of its ex-dividend date, single-handedly cushioning the benchmark while the rest of the tech complex bled.
Institutional flows: NT$79.1B out the door
All three institutional categories sold, and the foreign number was substantial:
| Investor category | Net trading value (Sept 15) |
|---|---|
| Foreign investors | -NT$62.70B (net sell) |
| Investment trusts | -NT$2.22B (net sell) |
| Dealers (proprietary + hedge) | -NT$14.21B (net sell) |
| Three institutions combined | -NT$79.12B |
A NT$62.7B single-day foreign disposal is a serious flow event, and it landed in tandem with currency pressure — USD/TWD rose 0.47% to 31.83, with the pair trading in a 31.70–31.85 range as Asian currencies broadly softened on outflows.
Beneath the index: rotation, not capitulation
The damage was concentrated in the expensive end of tech. MediaTek (2454) fell 2.85% to NT$4,430 — it entered the session at a 75.3x trailing PER, the richest of the big caps — while UMC (2303) dropped 2.81% to NT$138.50 and Hon Hai (2317) eased 0.80% to NT$246.50. ASE Technology (3711) lost 3.26%, and memory suppliers took the worst of the U.S. spillover, with AP Memory (6531) down more than 7% and Etron, Team Group, and ChipMOS all off over 2%.
Yet the exchange’s Semiconductor sub-index actually closed up 0.54% — a testament to TSMC’s weighting — and money visibly rotated toward domestic and defensive corners: Shipping gained 1.48% and Financials & Insurance rose 1.10%. Delta Electronics (2308) advanced 3.08% on strong monthly revenue. Cybersecurity names HwaCom (6148) and Sysware (2468) went limit-up after Nvidia CEO Jensen Huang’s remarks on AI cybersecurity applications, and silicon wafer makers GlobalWafers, Wafer Works, and Sino-American Silicon traded higher. Century (5314) locked limit-down on profit-taking.
Leverage and short positioning (Monday’s data)
The exchange’s leverage figures run a session behind, so these describe Monday’s positioning, published today. Market-wide margin purchase balance — retail leveraged longs — stood at NT$583.9B, down NT$3.99B on the day. Retail is trimming leverage into weakness rather than adding, which is the healthier configuration.
In the securities lending (SBL) channel — the institutional short book, distinct from retail margin shorts — balances rose in 547 shortable issues and fell in 361 on Monday. Among the majors, UMC’s SBL balance rose 2.11M shares (a build that preceded Tuesday’s 2.81% drop), TSMC’s rose a modest 292k shares, while Hon Hai saw 7.73M shares of covering. On the retail margin side, TSMC’s margin purchase balance ticked up 313 lots against a zero margin-short balance — small dip-buying, no retail short pressure.
One cross-market note: TSMC’s ADR closed Monday’s U.S. session at $418.01, leaving the gap over Tuesday’s Taipei close near 11.6% — below the roughly 15–25% structural premium the ADRs have carried in recent years. The two closes come from different sessions, so this mostly reflects the ADR absorbing Monday’s semiconductor rout before Taipei traded; it is a gauge of how much of the U.S. move Taipei has already priced, not a mispricing.
Macro backdrop
The valuation headwinds are real: the U.S. 10-year Treasury yield has surged to 5.0%, near a three-year high, and crude is holding above $100 a barrel — a difficult mix for long-duration tech multiples, with the Federal Reserve’s rate decision approaching. One tentative positive: S&P 500 futures recovered 0.49% to 7,662.50 during Asian hours, suggesting Monday’s AI-driven selloff may not extend unchecked into Tuesday’s U.S. session.
What to watch
- Wednesday, Sept 16 — TAIFEX TX futures and options final settlement. Third-Wednesday settlement can distort index-heavyweight order flow around the open; read Wednesday’s tape with that in mind.
- Thursday, Sept 17 — CBC quarterly board meeting (expected). With USD/TWD at 31.83 and a NT$62.7B foreign outflow in one session, the central bank’s read on currency and capital flows carries extra weight this quarter.
- Foreign flow follow-through. One NT$62.7B sell day is a data point; a second consecutive heavy outflow, especially alongside further TWD weakness into the Fed decision, would mark a trend change worth respecting.
Disclaimer: This is an information and analysis publication, not investment advice. See our Methodology for data sources, standards, and our corrections policy.