Is the Christian faith growing or shrinking?

Two case studies are instructive. In 1900, Christians comprised 9 percent of the African population and were outnumbered by Muslims four to one. Today, Christians comprise 44 percent of the population,15 and in the 1960s passed Muslims in number.16 This explosive growth is now beginning in China.17 Christianity is growing not only among the peasantry, but also among the social and cultural establishment, including the Communist party. At the current rate of growth, within thirty years Christians will constitute 30 percent of the Chinese population of 1.5 billion. — The Reason for God (Timothy Keller)