Wiener Börse confirms ATX reshuffle with new entrants STRABAG and PORR, effective September 2025

Wiener Börse confirms ATX reshuffle with new entrants STRABAG and PORR, effective September 2025

(IN BRIEF) Wiener Börse AG has announced the outcome of its semi-annual index review, confirming that STRABAG SE and PORR AG will be added to Austria’s leading ATX index, replacing Telekom Austria AG and Mayr-Melnhof Karton AG. Alongside these changes, PORR AG’s free float factor will be increased from 0.5 to 0.6, and Palfinger AG’s from 0.4 to 0.5. The ATX composition is determined by liquidity and free float capitalisation, and the new adjustments will take effect on 22 September 2025. Regular reviews of calculation parameters occur quarterly, with the next index composition review scheduled for March 2026.

(PRESS RELEASE) VIENNA, 3-Sep-2025 — /EuropaWire/ — The Index Committee of Wiener Börse AG has completed its semi-annual review of Austrian indices, resulting in adjustments to the country’s benchmark ATX. Effective 22 September 2025, STRABAG SE and PORR AG will join the ATX, replacing Telekom Austria AG and Mayr-Melnhof Karton AG. The inclusion of companies in the ATX is determined by a transparent methodology that considers both the average daily trading turnover (liquidity) and the size of the company’s free float capitalisation.

As part of this review, PORR AG’s free float factor will increase from 0.5 to 0.6, while Palfinger AG will see its free float factor rise from 0.4 to 0.5. The free float factor reflects the proportion of shares available for trading in the market, with holdings below 4% considered as free float. Higher factors translate into greater weighting of the share within the index.

The ATX calculation follows a rules-based approach laid out in the official guidelines for Austrian indices. The Index Committee, which includes institutional investors, trading members, issuers of financial products, academics, and representatives of Wiener Börse, makes decisions on index rules and composition. Index calculation parameters such as the number of shares, free float factors, and representation factors are reviewed quarterly, while the ATX composition itself is reassessed twice per year in March and September. The next scheduled review of Austrian indices will take place in March 2026, with free float factors due for reassessment in December 2025.

Wiener Börse also publishes a monthly “ATX watchlist,” providing a ranking of stocks based on liquidity and capitalised free float, giving investors and market participants early insight into potential changes.

About Wiener Börse AG

As the main provider of market infrastructure in the region, Wiener Börse AG is the gate to global markets. Uniting the stock exchanges in Vienna and Prague, the group offers state-of-the-art systems, information and IT services. Listed companies receive maximum liquidity and investors benefit from fast and cost-effective trading by the market leader. Wiener Börse AG also collects and distributes stock market data and calculates the most important indices of the region. Because of this unique know-how the national stock exchanges in Budapest, Ljubljana and Zagreb trust its IT services. Additionally, the group holds stakes in energy exchanges and clearing houses.

Exclusion of Liability

This press release may contain certain forward-looking statements and forecasts that are based on assumptions current made at the time of publication of this press release. We do not assume any liability for these forward-looking statements materializing. Furthermore, we would like to explicitly point out that this press release cannot serve as a basis for investment decisions and may not be construed as a solicitation to buy or a recommendation to invest by Wiener Börse AG. No liability is assumed for the information given in this press release.

Media Contacts:

Julia Resch
Head of Corporate Communications & Marketing, Spokesperson
email: julia.resch​(a)​​wienerboerse.at
Tel: +43 1 531 65-186

Alexander Wastl
Corporate Communications & Marketing
Email: alexander.wastl​(a)​wienerboerse.at
Tel: +43 1 531 65-153

SOURCE: Wiener Börse AG