Arizona has the Arizona Stock Exchange, formed in 1990. The exchange is an electronic call market which trades equity securities, including many Arizona-based companies. AZX conducts single-price auctions, of NYSE, NASDAQ, and AMEX securities, in what is often called "Dutch Auctions." In 1997, securities transactions were conducted by approximately 832 broker-dealer companies with 6,905 employees. There are 158 investment advisory organizations in Arizona. A total of 68 NASDAQ companies are headquartered in Arizona, and nine NASDAQ market makers. Four companies incorporated in Arizona are listed on the NYSE; including CSK Auto Corp., Pinnacle West Capital Corp., Simula, Inc., and Unisource Energy Corp.