The Wiener Börse AG is a bourse situated in Vienna, Austria. The exchange owns and operates the Prague Stock Exchange, and holds stakes in energy exchanges and clearing houses. It provides market infrastructure to other exchanges in Central, Eastern, and Southeastern Europe, and collects and distributes stock market data and calculates the most important indices of the region. The Austrian Traded Index (ATX), the leading index of Wiener Börse, tracks the price of its blue chips in real time. The ATX composition is updated every March and September, mainly based on a stock's capitalized free float and trading volumes. The Vienna Stock Exchange also maintains a market for fixed income securities, with more than 13,000 active bonds from 38 countries and a total volume of €720bn as at May 2023.