Flag of the Hong Kong region, China

Hong Kong is a special administrative region of China. With 7.4 million residents in a 1,104-square-kilometre (426 sq mi) territory, Hong Kong is the fourth most densely populated region in the world. Hong Kong was established as a colony of the British Empire after the Qing dynasty ceded Hong Kong Island in 1841–1842 as a consequence of losing the First Opium War. The colony expanded to the Kowloon Peninsula in 1860 and was further extended when the United Kingdom obtained a 99-year lease of the New Territories in 1898. Hong Kong was occupied by Japan from 1941 to 1945 during World War II. The territory was handed over from the United Kingdom to China in 1997. Hong Kong maintains separate governing and economic systems from that of mainland China under the principle of one country, two systems. Originally a sparsely populated area of farming and fishing villages, the territory is now one of the world's most significant financial centres and commercial ports. Hong Kong is the world's third-ranked global financial centre (behind New York City and London), ninth-largest exporter, and eighth-largest importer. Its currency, the Hong Kong dollar, is the ninth most traded currency in the world. Home to the second-highest number of billionaires of any city in the world, Hong Kong has the largest number of ultra high-net-worth individuals. Although the city has one of the highest per capita incomes in the world, severe income inequality exists among the population. Despite being the city with the most skyscrapers in the world, housing in Hong Kong is consistently in high demand. Hong Kong is a highly developed territory and has a Human Development Index (HDI) of 0.956, ranking fourth in the world and currently the only place in Asia to be in the top 5. The city has the highest life expectancy in the world, and a public transport usage exceeding 90 per cent.