Hong Kong, officially the Hong Kong Special Administrative Region of the People's Republic of China, is an autonomous territory on the Pearl River Delta of China. Macau lies across the delta to the west, and the province of Guangdong borders the territory to the north. With a total land area of 1,106 square kilometres (427 sq mi) and a population of over 7.3 million of various nationalities, it ranks as the world's fourth most densely populated sovereign state or territory. Hong Kong is one of the world's most significant financial centres, with the highest Financial Development Index score and consistently ranks as the world's most competitive and freest economic entity. As the world's 8th largest trading entity, its legal tender, the Hong Kong dollar, is the world's 13th most traded currency. It's also a member of the World Trade Organization (WTO) and the Asia-Pacific Economic Cooperation (APEC). Hong Kong's tertiary sector dominated economy is characterised by simple taxation with a competitive level of corporate tax and supported by its independent judiciary system. However, while Hong Kong has one of the highest per capita incomes in the world, it suffers from severe income inequality. Hong Kong is renowned for its deep natural harbour, which enables ready access by international cargo ships, and its impressive skyline, with a very high density of skyscrapers; the territory boasts the largest number of high rises of any city in the world. It has a very high Human Development Index ranking and the world's longest life expectancy.