As a city-state, Singapore is one of the world's most densely populated countries with about 12,000 people per sq mi (about 4,600 people per sq km). A massive urban renewal program, begun in the 1960s, has replaced virtually all of Singapore's slums with modern housing units. As a result of family planning and a strict immigration policy, the annual rate of population increase has declined to just over 1%, down from 4.5% in the 1950s. The population is over 75% Chinese; the largest minorities are Malays (14%) and South Asians (8%). Buddhism, Islam, Taoism, Hinduism, and Christianity are the main religions of Singapore. The country has four official languages: Mandarin, English, Malay, and Tamil.