WBI (Wiener Borse Index): What It Measures and How It Is Built

Direct Answer

The WBI (Wiener Borse Index) is the broadest Austrian equity benchmark, covering all securities listed on the regulated market of Wiener Borse. Administered by Wiener Borse AG, it applies free-float-adjusted market-capitalisation weighting and serves as the widest measure of the Austrian equity market, broader than the ATX Prime and ATX.

What this index covers

The WBI (Wiener Borse Index) covers the Austria equity market through the Vienna Stock Exchange (Wiener Borse). Wiener Borse AG 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 securities listed on the regulated market of Wiener Borse that meet the minimum free-float criteria set in the Wiener Borse published methodology. This is a wider universe than the prime market alone, which is the ATX Prime's scope.

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 across all qualifying regulated-market securities, per the Wiener Borse 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 WBI (Wiener Borse Index), the relevant market is the Vienna Stock Exchange (Wiener Borse) and the administrator is Wiener Borse AG. Per the published Wiener Borse AG methodology (verification date: August 31, 2026), the eligible universe is defined as: All securities listed on the regulated market of Wiener Borse that meet the minimum free-float criteria set in the Wiener Borse published methodology. This is a wider universe than the prime market alone, which is the ATX Prime's scope.

Reconstitution schedule

Entry and exit are governed by listing status on the regulated market. The index is adjusted on a continuous basis for corporate actions and on the ATX quarterly review schedule for planned reconstitution.

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

Reference for the full Austrian listed-equity market; used by total-market mandates and as a coverage benchmark against which sector and size indexes within the ATX family can be compared.

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 WBI (Wiener Borse Index) is most often compared with:

• ATX Prime: limited to the prime-market segment; the WBI includes the full regulated market.
• ATX: blue-chip flagship selecting the most liquid prime-market securities; the WBI includes the full breadth of regulated listings.

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

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

Current WBI (Wiener Borse Index) constituents

Wiener Borse AG publishes and licenses the WBI (Wiener Borse Index) constituent list. Swoopr does not republish it here. The provider's own page is the authoritative source for current membership and weights.

Wiener Borse AG: official WBI (Wiener Borse Index) 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