As one of the world’s leading international financial centres, Hong Kong has a major capitalist service economy characterised by low taxation and free trade, and the currency, Hong Kong dollar, is the ninth most traded currency in the world. The lack of space caused demand for denser constructions, which developed the city to a centre for modern architecture and the world’s most vertical city. The dense space also led to a highly developed transportation network with public transport travelling rate exceeding 90 percent, the highest in the world.