Direct Answer
The KRX 300 is a rule-based measurement of Korean broad equity benchmark, maintained by Korea Exchange. 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 KRX 300 covers Korean broad equity benchmark, within the South Korea market. Korea Exchange 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 300 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
Float adjusted market capitalisation weighted with no weight cap, calculated every second, with a base value of 1,000 at January 4, 2010 and a launch date of February 5, 2018.
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 universe is the KRX LargeMidCap TMI constituents across KOSPI and KOSDAQ, excluding REITs, social infrastructure companies and companies with impaired capital. Within each of ten GICS based sectors, companies are taken in market capitalisation order up to 80% of the sector total or the top 30% by rank, and dropped if outside the top 80% by trading value. The total is then set to 300.
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
Companies listed for less than six months on the screening base date are ineligible, with exceptions for KOSDAQ to KOSPI transfers whose combined listing exceeds six months and for spin-off or exceptional addition cases.
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
Reconstituted twice a year, effective the trading day after the last trading day of the June and December KOSPI 200 futures delivery month. Constituents are confirmed in May and November after the Index Committee 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 index keeps no replacement pool, so a removed constituent is not backfilled from a reserve list. A stock in the top 100 by market capitalisation among eligible securities can be added ahead of the sector filters, considering sector balance and liquidity, and replaces the smallest selected company.
References
- Korea Exchange: Korea Exchange, KRX 300 Methodology, as published 2025. Every rule described on this page is taken from this document.
Current KRX 300 constituents
Korea Exchange publishes and licenses the KRX 300 constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights.
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 KRX 300?
Korea Exchange maintains the KRX 300 and publishes the methodology document that defines its eligibility and weighting rules.
What does the KRX 300 measure?
It measures Korean broad 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 KRX 300 constituents?
Korea Exchange publishes the current constituent list. Swoopr does not republish it, because index providers license constituent data and Swoopr holds no such licence.