The TAIEX surged 7.98% to 43,119.75 on Friday, recovering a large slice of a five-session, near-11% plunge. Foreign investors net bought NT$67.55 billion as TSMC, MediaTek and UMC closed at or near their 10% daily limits.
After a two-day, 3,595-point rout, the TAIEX fell to 39,404 and then rallied more than 1,000 points intraday, closing at 39,933.30 (-0.26%) as UMC’s earnings-driven surge offset another NT$48.3B of foreign selling.
TSMC carries roughly 35% or more of the TAIEX’s capitalization weight, so a 1% move in the stock mechanically shifts Taiwan’s benchmark by about 0.35 percentage points before any other share trades. Here is how to decompose any TAIEX session into its TSMC and non-TSMC components — with worked examples from real July 2026 data.
Taiwan’s benchmark fell 3.76% to 40,039.18 on Wednesday, its fourth straight decline, as skepticism over AI infrastructure returns hit semiconductors. Foreign investors sold NT$22.25B in cash equities while investment trusts bought against the tide.
The TAIEX fell 1,195.97 points to 43,654.84 on Friday as a Wall Street rout over AI spending and $100 oil hit Taipei. Foreign investors sold a net NT$60.95 billion in cash equities, with UMC down 7.6% and MediaTek off 3.2%.
Taiwan’s benchmark closed barely changed Thursday after a whippy session that briefly reclaimed 45,000. All three institutional groups bought — foreign investors for a second day — even as the previous session’s futures book showed foreigners still heavily net short.
The TAIEX rose 1.34% to 44,825.78 on Wednesday as foreign investors and investment trusts bought nearly NT$17B each — but TSMC sat out, and MediaTek, UMC and Hon Hai carried the tape.
The TAIEX surged 4.20% to 44,232.87 on Tuesday, clawing back part of Friday’s historic 6.47% rout. But the rebound was domestically funded: investment trusts bought NT$17.23B while foreign investors stayed net sellers at NT$-4.33B.
The TAIEX gave back an early bounce to close down 0.52% at 42,449.70 in the first session after Friday’s record plunge. TSMC rose on a $100B Arizona expansion, but UMC cratered 9.7%, foreigners kept selling, and investment trusts did the buying.
Taiwan’s benchmark fell 6.47% to 42,671 on Friday as an overnight 4.29% rout in the Philadelphia Semiconductor Index swept through Taipei. TSMC dropped 7.29% despite a record Q2, UMC closed limit-down, and foreign investors had already sold NT$48.3 billion of cash equities heading into the session.