ISEQ All Share: What It Measures and How It Is Built

Direct Answer

The ISEQ All Share covers all equities listed on Euronext Dublin (formerly the Irish Stock Exchange) that meet the minimum eligibility criteria in Euronext's published methodology. Broader than the ISEQ 20, it provides a complete picture of the Irish listed equity market by including mid-cap and smaller companies beyond the headline 20.

What this index covers

The ISEQ All Share covers the Ireland equity market through the Euronext Dublin. Euronext defines which securities are eligible, how they are selected from that pool and how much each contributes to the published number.

The eligible universe is: All equities listed on Euronext Dublin meeting the minimum free-float, liquidity and market-capitalisation criteria specified in the Euronext published index methodology.

Understanding the eligible universe is the most important step in understanding what an index measures. An index that selects by listing venue will behave differently from one that selects by company domicile, and a sector index will have very different risk characteristics from a broad market measure even if they share some constituents.

How constituents are weighted

Free-float-adjusted market-capitalisation weighting, per the Euronext published methodology.

Weighting is the mechanism that translates a list of companies into a single number. Free-float-adjusted market-capitalisation weighting is the most common method: larger companies contribute more to the index level than smaller ones, and the free-float adjustment excludes shares that are not available to public investors (such as government-held strategic stakes or closely-held founder shares). This makes the index level reflect the actual investable market rather than total market size.

Eligible universe and eligibility rules

Eligibility rules determine which companies can be included at a review and which must exit. The key dimensions to verify are: which exchange or market segment is in scope; whether domicile or listing venue determines eligibility; the minimum free-float threshold; the liquidity screen; and whether there are sector restrictions.

For the ISEQ All Share, the relevant market is the Euronext Dublin and the administrator is Euronext. Per the published Euronext methodology (verification date: August 31, 2026), the eligible universe is defined as: All equities listed on Euronext Dublin meeting the minimum free-float, liquidity and market-capitalisation criteria specified in the Euronext published index methodology.

Reconstitution schedule

Quarterly, aligned with the ISEQ family review schedule.

Reconstitution is the date on which the index changes shape by design rather than by price. Passive funds tracking the index must trade toward the new membership list, which creates predictable order flow around the review date. Active managers often position around reconstitution events to capture or avoid that flow.

How investors use this index

Broad Irish equity benchmark; provides total-market coverage beyond the ISEQ 20 blue chips; used for attribution analysis of the full Irish listed market.

For any index, three uses are distinct: as a performance benchmark (measuring how well a portfolio did relative to the market), as a product underlying (an ETF or structured product replicating the index), and as a research reference (tracking market-cap, sector weights or concentration over time). The same index can serve all three purposes, but the choice of which to use depends on the investment mandate and the specific question being answered.

Comparisons with related indexes

The ISEQ All Share is most often compared with:

• ISEQ 20: selects only the 20 largest Irish companies; ISEQ All Share includes the full eligible universe.
• ISEQ Small: the smaller-cap tier of the Irish market; ISEQ All Share covers all tiers including large, mid and small.

When switching from one benchmark to another, the practical question is what changes in coverage: does the alternative add smaller companies, exclude a sector, change the weighting method or extend to a different currency? Each of these changes alters what the index can tell you about market performance.

References

• Euronext: Index Products, as published per the provider's methodology page. All methodology claims on this page are derived from this source.

Current ISEQ All Share constituents

Euronext publishes and licenses the ISEQ All Share constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights.

Euronext: official ISEQ All Share page

Related reading

• All stock market indexes: how indexes are built, weighted and revised.
• European Stock Market 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