The Wiener Börse AG is a bourse situated in Vienna, Austria. The exchange also owns and operates the Prague Stock Exchange, 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. Additionally, the group holds stakes in energy exchanges and clearing houses. Apart from traditional exchange operations, new lines of business have been established in the past years such as data vending, index calculation, and providing IT services to other exchanges in Central and Eastern Europe. The Austrian Traded Index, the leading index of Wiener Börse, tracks the price trends of the blue chips on Wiener Börse in real time. The composition of the ATX is reviewed every year in March and September. The main criteria for inclusion or deletion are the capitalized free float and stock exchange trading volumes.