Chad is a religiously diverse country. Various estimates, including from Pew Research Center in 2010, found that 52–58% of the population was Muslim, while 39–44% were Christian. 22% were Catholic and a further 17% were Protestant. Among Muslims, 48% professed to be Sunni, 21% Shia, 4% Ahmadi and 23% non-denominational Muslim. A small proportion of the population continues to practice indigenous religions. Animism includes a variety of ancestor and place-oriented religions whose expression is highly specific. Islam is expressed in diverse ways; for example, 55% of Muslim Chadians belong to Sufi orders. Christianity arrived in Chad with the French and American missionaries; as with Chadian Islam, it syncretises aspects of pre-Christian religious beliefs. Muslims are largely concentrated in northern and eastern Chad, and animists and Christians live primarily in southern Chad and Guéra. The constitution provides for a secular state and guarantees religious freedom; different religious communities generally co-exist without problems.