A 700-point intraday slide breaks the monthly average
The TAIEX dropped 322.33 points, or 0.70%, to close Monday at 45,862.52, surrendering the 46,000 level and its monthly moving average. The session was worse than the close suggests: the index opened down 174.11 points at 46,010.74 and at one stage was off more than 700 points at an intraday low of 45,398, before dip-buying trimmed the damage into the 13:30 close. Turnover was NT$630.92 billion.
Three catalysts did the work. Calls from AI model developers to slow the pace of frontier model development raised questions about near-term enterprise AI capex and the Taiwan supply chain that feeds it. Markets also moved to price a possible rate hike at the September 15–16 FOMC meeting, a repricing reinforced by elevated crude prices after a drone and missile strike on a Saudi oil pipeline. The result was a sharp decoupling from Friday’s US session, where the Philadelphia Semiconductor Index rose 1.81% to 11,824.00 and the S&P 500 added 0.86% to 7,656.98. S&P 500 futures trading down 0.66% at 7,608.75 during Taipei hours confirmed that Monday’s Asian risk-off was leading, not lagging, the global tape.
Heavyweights: TSMC leads the downside, but the damage is narrow
TSMC (2330) fell NT$30, or 1.24%, to NT$2,380 and was the main drag on the index. MediaTek (2454) lost 0.55% to NT$4,560. Hon Hai (2317) bucked the trend, edging up 0.20% to NT$248.50, and UMC (2303) rose 1.42% to NT$142.50. Notably, the TWSE semiconductor subindex actually gained 1.10% on the day — Monday’s selling was concentrated in the mega-cap AI names and in specific casualties, not the sector broadly. Optical lens makers Largan Precision (3008) and Genius Electronic Optical (3406) both closed limit-down after foreign brokerage downgrades, while memory and second-tier foundry names such as Winbond and Powerchip saw heavy selling.
The defensive rotation was equally clear on the other side: financials and insurance rose 1.94%, the day’s standout sector, with foreign inflows reported into lenders including Taichung Commercial Bank (2804) and KGI Financial (2883). Shipping was flat at +0.13%, with container carrier Yang Ming (2609) drawing foreign accumulation.
| Stock | Close (9/14) | Change | PER (9/11) | Foreign ownership |
|---|---|---|---|---|
| TSMC (2330) | 2,380.00 | -1.24% | 27.94 | 69.27% |
| MediaTek (2454) | 4,560.00 | -0.55% | 75.72 | 55.97% |
| Hon Hai (2317) | 248.50 | +0.20% | 16.35 | 40.35% |
| UMC (2303) | 142.50 | +1.42% | 21.13 | 41.06% |
Institutional flows: foreigners sell NT$36.96 billion
Official TWSE data for Monday’s session show all-around institutional selling:
- Foreign investors: net SELL NT$36.96 billion
- Investment trusts: net BUY NT$2.35 billion
- Dealers (proprietary + hedge): net SELL NT$15.09 billion
- Three institutions combined: net SELL NT$49.70 billion
The pattern is familiar late-cycle behavior: foreign money reducing index-heavy semiconductor exposure while selectively adding financials and shipping, with domestic trusts providing a modest bid against the flow.
Leverage and shorts — Friday’s positioning data
Margin and securities-lending figures run a session behind, so the latest prints cover Friday, September 11 — the setup going into Monday, not Monday itself. Market-wide margin purchase balances (retail leveraged longs) stood at NT$587.9 billion, down NT$4.03 billion on the day — retail was already trimming leverage before Monday’s break. In the institutional short channel, SBL balances rose in 481 shortable issues and fell in 393, a mild tilt toward building shorts.
At the stock level, the Friday data cut both ways. Hon Hai saw a substantial 3.73 million-share reduction in its SBL short balance alongside a 1,041-lot drop in retail margin longs — short covering that helps explain its resilience Monday. UMC also saw shorts trimmed in both channels. Against that, Delta Electronics’ SBL balance rose by 446,000 shares, and TSMC’s retail margin balance ticked up 427 lots even as its margin short balance went to zero — retail was leaning long the index heavyweight into a down session.
Currency: a twin sell-off, and a note on the ADR gap
The Taiwan dollar weakened alongside equities, with USD/TWD up 0.34% at 31.74. The pair opened at 31.65, touched 31.726 intraday, and stood at 31.717 at the midday interbank close on US$693 million of volume — a classic equity-outflow/currency-weakness pairing consistent with the foreign cash-market selling.
TSMC’s ADR closed Friday in New York at $433.24, roughly 15.6% above Monday’s Taipei close on an adjusted basis. That gap sits near the low end of the structural 15–25% premium the ADRs have carried in recent years, and it compares closes from different sessions — it is a feature of limited fungibility, not a mispricing. What matters is how the gap moves once New York reopens after Monday’s Taipei decline.
What to watch
- FOMC, September 15–16. Rate-hike repricing was a primary driver of Monday’s selloff; the statement and dots will set the tone for foreign flows the rest of the week.
- TAIFEX final settlement, Wednesday, September 16. Third-Wednesday futures and options settlement lands the morning after the Fed, raising the odds of exaggerated index swings around the open.
- CBC quarterly board meeting, expected Thursday, September 17. With USD/TWD pushing toward 31.75 in a twin sell-off, the central bank’s read on the currency and rates follows straight on the Fed’s heels.
Disclaimer: This is an information and analysis publication, not investment advice. See our Methodology for data sources, standards, and our corrections policy.