Pakistan has one of the world's most rapidly growing populations. Its people are a mixture of many ethnic groups, a result of the occupation of the region by groups passing through on their way to India. The Pathans (Pashtuns) of the northwest are a large, indigenous group that has long resisted advances by invaders and that has at times sought to establish an autonomous state within Pakistan. Baluchis, who live mainly in the southwest, have also pressed for the creation of a state that would incorporate parts of Afghanistan and Iran. Punjabis reside mainly in the northeast, and Sindhis in the southeast. Pakistan is an overwhelmingly (about 97%) Muslim country; about three fourths of the Muslims are Sunnis (largely Sufis) and the rest Shiites. Urdu is the official language, but Punjabi, Sindhi, Pashto, Baluchi, Hindko, and Brahui are also spoken; English is common among the upper classes and in the government.