Mandarin Chinese is the majority language in most of mainland China, though there are many ethnic minority groups. Explosive growth has characterized the church for at least the past 30 years. About 100 million Christians live in China, but only 30 million are affiliated with the government-authorized Three-Self Patriotic Movement (TSPM), the state church controlled by the communist government. The remaining 70 million worship in unapproved house churches. Despite continual pressure and oppression from the communist government, house church leaders refuse to compromise the gospel and join government- approved churches. About 60 percent of believers in China live in rural areas. Few house church leaders have formal theological training or access to Bible study materials. Because of decades of atheistic communist belief promoted by the government, most Chinese are nonreligious, though about 20 percent are Buddhist and another 20 percent practice Chinese folk religion. The main persecutor is the government.