TSMC Is 42% of Taiwan: When Your Asia Fund Becomes a TSMC Fund — The Concentration Math

Track 2 Tactical Allocator｜2026-09-26｜Lead Financial Strategist, mpf.hk

On 23 September, Taiwan’s Weighted Index closed above 48,000 for the first time: 48,157.29, an all-time high. On the same day, TSMC hit NT$2,500 — also an all-time high.

The next day (24 September), the index gave back 0.4% to 47,949. TSMC fell 0.6%. One company’s rise and fall dragging the whole market — that is not a metaphor, it is arithmetic: TSMC accounts for roughly 42% of the Taiwan Weighted Index (Bloomberg, May 2026; TradingEconomics put it at “more than 40%” on 24 September). In the MSCI Taiwan Index, its weight is higher still: 58.33% (MSCI semi-annual review). One index, more than half of it a single stock.

For MPF members, the question is concrete: you thought you bought an “Asia-Pacific equity fund” spread across a dozen markets. What you actually bought is a TSMC amplifier.

The macro matrix: a single bet with an AI tailwind

First, the scale of this rally. From the 30 July trough of 39,933.3 to 48,157.29 on 23 September, the Taiwan Weighted Index gained about 20.6% in seven weeks. TSMC is up roughly 49% year-to-date, and its market value has lifted Taiwan’s stock market to the world’s fifth largest (about US$4.95 trillion, overtaking India’s US$4.92 trillion in May, per Bloomberg data).

More notable is the structural bid: Taiwan’s financial regulator raised the single-stock cap for domestic funds from 10% to 25% of net assets (for companies with index weights above 10% — currently only TSMC qualifies). JPMorgan estimates this could bring more than US$6 billion of fresh inflows. In other words, the concentration is not an accident; it is partly by regulatory design. Every fresh inflow that must buy TSMC to stay benchmark-neutral pushes the weight higher, and a higher weight forces more benchmark-hugging buying — a concentration flywheel that runs until something breaks it. Record highs are when that flywheel spins fastest.

But concentration math cuts both ways. On one record day in May, TSMC’s gains alone contributed more than 1,100 points of the index’s 1,778-point single-day move. In reverse, on 24 September TSMC’s 0.6% fall dragged electronic technology down 0.4% and snapped a six-session winning streak. You enjoyed the 49% upside — be ready for the other side of the volatility.

The backtest spine: how one stock captures an index

A 58.33% TSMC weight in the MSCI Taiwan Index is a number worth pausing on. It means:

• TSMC up 10% lifts the index by about 5.8 percentage points on its own — the other 76 constituents combined matter less than this one company;
• TSMC down 10% drags the index down about 5.8 percentage points — your “diversification” diversifies almost nothing.

Now look at what MPF members actually hold. Most MPF Asia-Pacific ex-Japan equity funds track the MSCI AC Asia ex Japan Index, where Taiwan’s weight is about 27.16% (MSCI semi-annual review). Multiply: 27.16% x 42% = roughly 11.4% — of every HK$100 in your Asia fund, HK$11.40 is TSMC.

Illustrative sandbox: an MPF balance of HK$1 million, with 40% (HK$400,000) in an Asia-Pacific equity fund:

• Single-stock exposure: HK$400,000 x 11.4% = about HK$45,600 in TSMC;
• If TSMC corrects 20% (a normal swing for a cyclical semiconductor stock): that HK$45,600 loses HK$9,100 — nearly 1% of your entire MPF balance wiped out by one company’s share price.

For perspective: every other Taiwanese company in the same fund adds up to about 15.8% (27.16% x 58%). One company versus every other listed company in an economy — that is the true face of concentration.

The execution blueprint (illustrative): count your TSMC

Step one: open your fund fact sheet and find two numbers — the “Taiwan” weight in the country/region allocation, and whether TSMC appears in the top-10 holdings. Many Greater China equity funds carry Taiwan exposure too — do not assume only Asia-Pacific funds are affected.

Step two: do the multiplication above. Fund Taiwan weight x 42% = your TSMC coefficient. If it exceeds 10%, understand that you effectively hold a semiconductor single-stock fund, just packaged and priced as a regional fund.

Step three: discipline, not prediction. MPF runs on T+1/T+2 forward pricing — chasing the record high you saw on 23 September buys you the price of the 24th or 25th, after the pullback has already happened. Tilt your monthly contributions toward Japan or European equity funds to rebalance gradually, instead of switching on a big day. The tool for concentration risk is rebalancing, not timing.

One last number: 48,157 to 50,000 is 1,843 points. The market is already counting down to that milestone. The closer the milestone, the more people chase it, and the higher the concentration climbs — which is exactly when the math tells you to stay cool.

Sources: TradingEconomics (23–24 Sep 2026), Bloomberg via TradingView / PL Capital / Outlook Business (26 May 2026), MSCI semi-annual index review, JPMorgan. Illustrations only; past performance is not indicative of future results.