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