The economy of Hong Kong is a highly developed free-market economy, characterised by low taxation, almost free port trade and a international financial market. Its currency, called the Hong Kong dollar, is legally issued by three major international commercial banks, and is pegged to the US dollar. Interest rates are determined by the individual banks in Hong Kong to ensure they are market driven. There is no officially recognised central banking system, although the Hong Kong Monetary Authority functions as a financial regulatory authority.