--- title: "TUNINDEX20: Methodology" description: "TUNINDEX20 is maintained by Bourse de Tunis and covers top 20 companies listed on the Tunis Stock Exchange by market capitalisation. How it is weighted." canonical: https://www.getswoopr.com/stocks/indexes/tunindex20/ source: "Swoopr Investment: https://www.getswoopr.com" --- # TUNINDEX20: What It Measures and How It Is Built ## Direct Answer > The TUNINDEX20 is a rule-based measurement of top 20 companies listed on the Tunis Stock Exchange by market capitalisation, maintained by Bourse de Tunis. 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 TUNINDEX20 covers top 20 companies listed on the Tunis Stock Exchange by market capitalisation, within the Tunisia market. Bourse de Tunis 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 market capitalisation using the same calculation and publication rules as TUNINDEX, including the 15% cap on any one value and float rounded up to 10% steps. The index is of return type. 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 25 largest free float market capitalisations on the main market that trade continuously and have been listed over one month. The 15 largest meeting a minimum turnover rate are chosen, then five more from the remaining ten by combined rank on size, volume, turnover rate, trading frequency and spread. 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 newly introduced share has its turnover measured ten trading days after its first effective quotation, and it must meet the minimum turnover rate set at the annual review. 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 The regular review is held once a year in December, effective the first business day of January. Exceptional reviews in March, June and September take effect on the first business day of April, July and October. 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 At the quarterly exceptional reviews a constituent ranked below 25th by free float market capitalisation exits and the largest eligible outsider replaces it, and an eligible outsider ranked 15th or better enters and displaces the smallest constituent. ## References - [Bourse de Tunis: Bourse de Tunis Guide des indices boursiers](https://www.bvmt.com.tn/sites/default/files/documentation/indices/Guide-Indices-Boursiers.pdf), as published 2023. Every rule described on this page is taken from this document. ## Current TUNINDEX20 constituents Bourse de Tunis publishes and licenses the TUNINDEX20 constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights. [Bourse de Tunis: official TUNINDEX20 page](https://www.amf.org.ae/en/amf_indices/yearly) ## Related reading - [All stock market indexes](https://www.getswoopr.com/stocks/indexes/): how indexes are built, weighted and revised. - [Emerging Markets indexes](https://www.getswoopr.com/stocks/indexes/emerging-markets/): 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 TUNINDEX20? Bourse de Tunis maintains the TUNINDEX20 and publishes the methodology document that defines its eligibility and weighting rules. ### What does the TUNINDEX20 measure? It measures top 20 companies listed on the Tunis Stock Exchange by market capitalisation. 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 TUNINDEX20 constituents? Bourse de Tunis 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.