--- title: "WIG20: Methodology" description: "WIG20 is maintained by GPW Benchmark and covers Polish large-cap equity benchmark. How the index selects and weights its constituents, and what it measures." canonical: https://www.getswoopr.com/stocks/indexes/wig20/ source: "Swoopr Investment: https://www.getswoopr.com" --- # WIG20: What It Measures and How It Is Built ## Direct Answer > The WIG20 is a rule-based measurement of Polish large-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 WIG20 covers Polish large-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 20 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, so by free float market capitalization. A single company is reduced proportionally when its share of the index value exceeds 15%. WIG20 is a price index and excludes dividend income, while WIG20TR is the total return version that includes 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 20 large, liquid companies from the GPW Main List taken from one joint ranking shared with mWIG40, sWIG80 and WIG30, scored 40% on share of 12 month traded volume and 60% on share of free float value. Companies in the lowest quartile of free float capitalization are left out, a Monthly Turnover Ratio liquidity test applies, and no more than five companies may come from one exchange sector. 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 5% of the free float capitalization of all WIG20 companies, and the lowest ranked member leaves. Otherwise a new listing waits for a review. The liquidity test uses the last 12 full calendar months of trading. 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 uses data four weeks before the third Friday of March, June, September and December. The annual revision is in March and quarterly adjustments in the other three months, 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 Membership has an unconditional zone and a buffer zone. Ranks 1 to 15 are in and ranks 26 or lower are out at the annual March revision (1 to 10 and 31 or lower at quarterly adjustments); ranks in between are added or dropped only as needed to keep 20 members. ## References - [GPW Benchmark: GPW Benchmark, GPW Benchmark Indices, March 2026 edition (index profiles, calculation principles and periodic modifications)](https://www.gpwbenchmark.pl/pub/BENCHMARK/files/PDF/opis_indeksow/IndicesGPWB_0326.pdf), as published 2026. Every rule described on this page is taken from this document. ## Current WIG20 constituents GPW Benchmark publishes and licenses the WIG20 constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights. [GPW Benchmark: official WIG20 page](https://gpwbenchmark.pl/en-home) ## Related reading - [All stock market indexes](https://www.getswoopr.com/stocks/indexes/): how indexes are built, weighted and revised. - [Europe indexes](https://www.getswoopr.com/stocks/indexes/europe/): others covering the same region. - [Index concentration](https://www.getswoopr.com/technical-analysis/market-concentration/index-concentration/): measuring how much of an index sits in its largest holdings. - [Index rebalancing and inclusion effects](https://www.getswoopr.com/stocks/corporate-actions-catalysts/index-rebalancing-and-inclusion-effects/): what happens to a stock when index membership changes. ## Frequently Asked Questions ### Who maintains the WIG20? GPW Benchmark maintains the WIG20 and publishes the methodology document that defines its eligibility and weighting rules. ### What does the WIG20 measure? It measures Polish large-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 WIG20 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. ## About the author The [Swoopr Editorial Team](https://www.getswoopr.com/authors/swoopr-editorial-team/) writes Swoopr Investment's educational library, covering market structure, analysis methods and the mechanics behind the numbers investors read every day. Our [editorial policy](https://www.getswoopr.com/legal/editorial-policy/) and [corrections policy](https://www.getswoopr.com/legal/corrections-policy/) set out how this content is produced, reviewed and fixed when it is wrong.