Direct Answer
The FTSE TWSE Taiwan Mid-Cap 100 Index is a rule-based measurement of Taiwanese mid-cap equity benchmark, maintained by TWSE/FTSE Russell. Like every index it owns nothing: it is a number produced by applying a published weighting formula to a selected list of companies, revised on a schedule the provider sets.
What this index covers
The FTSE TWSE Taiwan Mid-Cap 100 Index covers Taiwanese mid-cap equity benchmark, within the Taiwan market. TWSE/FTSE Russell defines which securities are eligible, how they are selected from that pool, and how much each one contributes to the published number.
The name states a target of 100 companies. A target is not a guarantee of the exact count on any given day: corporate actions, dual share classes and pending additions all move the real number around it.
How constituents are weighted
Market capitalisation adjusted for free float and foreign ownership limits. Values are calculated in New Taiwan dollars in real time and published every five seconds.
The weighting method is the single biggest driver of how an index behaves. Two indexes covering the same market can diverge for years purely because they weight differently, which is why comparing index levels without knowing the method tells you very little.
What qualifies for inclusion
The next 100 companies by full market value outside the Taiwan 50 Index among eligible Taiwan Stock Exchange stocks. Full delivery stocks and investment trusts are ineligible, and a free float of 5% or below is excluded.
Eligibility rules are the part of an index most readers never look at and the part that decides what it can possibly measure. A screen that excludes a whole sector, or admits only one listing venue, shapes the result far more than any day of trading does.
How long a listing must exist first
New issues and newly eligible securities need a trading record of at least 20 days and a turnover of 0.050% of shares. Liquidity is tested annually in March using monthly median daily trading volume.
A seasoning rule is why a large new listing does not appear in an index the week it starts trading. It is a deliberate lag, and it means an index can under-represent a fast-growing part of the market for months at a time.
When the membership is revised
Quarterly reviews in March, June, September and December, using data from the Monday four weeks before the effective date, with changes applied after the close on the third Friday. A reserve list of the 10 highest ranked non-constituents is published after each review.
Reconstitution is the one date an index changes shape by design rather than by price. Funds tracking it have to trade toward the new membership, which is why the schedule matters to anyone holding the tracker rather than only to the provider.
The rule that surprises people
The count is fixed at 100 with a wide buffer: a company is inserted only if it rises to 130th or above and deleted only if it falls to 171st or below by full market value.
References
- TWSE/FTSE Russell: FTSE Russell FTSE TWSE Taiwan Index Series Ground Rules, as published 2026. Every rule described on this page is taken from this document.
Current FTSE TWSE Taiwan Mid-Cap 100 Index constituents
TWSE/FTSE Russell publishes and licenses the FTSE TWSE Taiwan Mid-Cap 100 Index constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights.
TWSE/FTSE Russell: official FTSE TWSE Taiwan Mid-Cap 100 Index page
Related reading
- All stock market indexes: how indexes are built, weighted and revised.
- Asia-Pacific indexes: others covering the same region.
- Index concentration: measuring how much of an index sits in its largest holdings.
- Index rebalancing and inclusion effects: what happens to a stock when index membership changes.
Frequently Asked Questions
Who maintains the FTSE TWSE Taiwan Mid-Cap 100 Index?
TWSE/FTSE Russell maintains the FTSE TWSE Taiwan Mid-Cap 100 Index and publishes the methodology document that defines its eligibility and weighting rules.
What does the FTSE TWSE Taiwan Mid-Cap 100 Index measure?
It measures Taiwanese mid-cap equity benchmark. The index is a calculated number applying a weighting formula to a selected list of companies, and it holds nothing itself.
Where can I see the current FTSE TWSE Taiwan Mid-Cap 100 Index constituents?
TWSE/FTSE Russell publishes the current constituent list. Swoopr does not republish it, because index providers license constituent data and Swoopr holds no such licence.