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. With a total land area of 1,106 square kilometers (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. Under the principle of "one country, two systems", Hong Kong maintains a separate political and economic system from China. Except in military defense and foreign affairs, Hong Kong maintains its independent executive, legislative and judiciary powers. Hong Kong is one of the world's most significant financial centers, with the highest Financial Development Index score and consistently ranks as the world's most competitive and freest economic entity.