Direct Answer
The mWIG40 is a rule-based measurement of Polish mid-cap equity benchmark, maintained by GPW Benchmark. 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 mWIG40 covers Polish mid-cap equity benchmark, within the Poland market. GPW Benchmark 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 40 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
Weighted by free float shares times price, with a single company reduced proportionally when it exceeds 10% of the index value. mWIG40 is a price index that leaves out dividend income, and mWIG40TR is the total return version including dividends and subscription rights.
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
40 medium sized companies from the GPW Main List chosen from the joint ranking, excluding WIG20 and sWIG80 participants and foreign companies listed on the GPW and elsewhere whose market capitalization at the ranking date is above 1 billion euros. The base criteria and the Monthly Turnover Ratio liquidity test also apply.
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
A large IPO is added between reviews if its free float capitalization at the IPO date is at least 2.5% of the free float capitalization of the mWIG40 companies, and the lowest ranked member leaves. Companies that enter through the fast track are exempt from the turnover ratio test for their first 12 months.
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
Ranking data comes from four weeks before the third Friday of March, June, September and December. March is the annual revision and the other months are quarterly adjustments, effective after the session on the third Friday and announced two weeks earlier.
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
Foreign companies whose market capitalization at the ranking date is above 1 billion euros are excluded, however high they rank, which keeps large cross listed names out of the mid cap index.
References
- GPW Benchmark: GPW Benchmark, GPW Benchmark Indices, March 2026 edition (index profiles, calculation principles and periodic modifications), as published 2026. Every rule described on this page is taken from this document.
Current mWIG40 constituents
GPW Benchmark publishes and licenses the mWIG40 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.
- Europe 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 mWIG40?
GPW Benchmark maintains the mWIG40 and publishes the methodology document that defines its eligibility and weighting rules.
What does the mWIG40 measure?
It measures Polish 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 mWIG40 constituents?
GPW Benchmark publishes the current constituent list. Swoopr does not republish it, because index providers license constituent data and Swoopr holds no such licence.