Hong Kong (香港, see Name section), alternatively known by its initials H.K., is a Special Administrative Region of the People's Republic of China situated on China's south coast and enclosed by the Pearl River Delta and South China Sea. The city is known for its expansive skyline and deep natural harbour. With a land mass of 1,104 km2 (426 sq mi) and a population of over seven million people, Hong Kong is one of the most densely populated areas in the world. Hong Kong's population is 93.6% ethnic Chinese and 6.4% from other groups. Hong Kong's Cantonese-speaking majority originate mainly from the neighbouring Canton (now Guangdong) province, from which many of them fled to escape wars and Communist rule in China from the 1930s to the 1960s.Hong Kong became a colony of the British Empire after the First Opium War (1839–42). Hong Kong Island was first ceded to the UK in perpetuity, followed by Kowloon Peninsula in 1860 and then the New Territories was put under lease in 1898. It was occupied by Japan during the Pacific War (1941–45), after which the British resumed control until 1997, when China resumed sovereignty. The region espoused minimum government intervention under the ethos of positive non-interventionism during the colonial era. The time period greatly influenced the current culture of Hong Kong, often described as "East meets West", and the educational system, which used to loosely follow the system in England until reforms implemented in 2009.On 1 July 1997, Hong Kong became the first Special Administrative Region of the People's Republic of China, under the principle of "one country, two systems" (the other, Macau, attained that status in December 1999).It has a different political system from mainland China. Hong Kong's independent judiciary functions under the common law framework. Hong Kong Basic Law, its constitutional document, which stipulates that Hong Kong shall have a high degree of autonomy in all matters except foreign relations and military defence, governs its political system. Although it has a burgeoning multi-party system, a small-circle electorate controls half of its legislature. The head of the government, the Chief Executive of Hong Kong, is chosen by an Election Committee of 400 to 1,200 members, a situation that will be in effect during the first 20 years of Chinese rule.Hong Kong is a world city. It is one of the Alpha+ cities. Also, a Time Magazine article in 2008 coined the phrase "Nylonkong", which referred to New York City, London and Hong Kong, that these three cities form a global network that facilitates the global economy. As Hong Kong ranks the third most important leading international financial centre, after London and New York City, Hong Kong has a major capitalist service economy characterised by low taxation and free trade, and the currency, Hong Kong dollar, is the eighth 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. Hong Kong has one of the highest per capita incomes in the world. The dense space also led to a highly developed transportation network with the public transport travelling rate exceeding 90 percent, the highest in the world. Hong Kong has numerous high international rankings in various aspects. For instance, its economic freedom, financial and economic competitiveness, quality of life, corruption perception, Human Development Index are all ranked highly. According to estimates from both UN and WHO, Hong Kong had the longest life expectancy of any region in the world in 2012. Hong Kong also has the highest average IQ score among 81 countries around the world.