There are no securities exchanges in Puerto Rico. Bonds issued by the Government Development Bank, exempt from federal income taxes and from the income taxes of all US states and cities, are offered for sale on the world securities market. The Puerto Rico Stock Index (PRSI) is a market-value-weighted index, composed of 10 businesses with their main headquarters or main places of business in Puerto Rico. The companies included in the index are traded on national stock markets, such as the NYSE and AMEX, and in the over-the-counter market (NASDAQ). There are several hundred broker-dealer firms registered to do business in Puerto Rico. Approximately 100 organizations providing security investment advice are registered in Puerto Rico.