The AEX index, derived from Amsterdam Exchange index, is a stock market index composed of Dutch companies that trade on NYSE Euronext Amsterdam, formerly known as the Amsterdam Stock Exchange. Started in 1983, the index is composed of a maximum of 25 of the most actively traded securities on the exchange. It is one of the main national indices of the stock exchange group NYSE Euronext alongside Brussels' BEL20, Paris's CAC 40 and Lisbon's PSI-20.