These are some of the key findings of a new report released by the Pew Research Center, called Global Christianity: A Report on the Size and Distribution of the World's Christian Population, which provides data on the world's Christian population by region, country and tradition.
Almost half (48 percent) of all Christians live in the 10 countries with the largest number of Christians. Three of the top 10 are in the Americas (the United States, Brazil and Mexico). Two are in Europe (Russia and Germany); two are in the Asia-Pacific region (the Philippines and China); and three are in sub-Saharan Africa (Nigeria, Democratic Republic of the Congo and Ethiopia), reflecting Christianity's global reach.
Christians are diverse theologically as well as geographically. About half are Catholic. Protestants, broadly defined, make up 37 percent. Orthodox Christians comprise 12 percent of Christians worldwide. Other Christians, such as Mormons and Jehovah's Witnesses, make up the remaining 1 percent of the global Christian population.
Taken as a whole, Christians are by far the world's largest religious group. Muslims, the second-largest group, make up a little less than a quarter of the world's population, according to previous studies by the Pew Forum.
Although Christianity began in the Middle East-North Africa, that region today has both the lowest concentration of Christians (about 4 percent) and the smallest number of Christians (about 13 million) of any major geographic region.
Although Christians comprise just under a third of the world's people, they form a majority of the population in 158 countries and territories, about two-thirds of all the countries and territories in the world.
Nigeria now has more than twice as many Protestants (broadly defined to include Anglicans and independent churches) as Germany, the birthplace of the Protestant Reformation.
About 90 percent of Christians live in countries where Christians are in the majority; only about 10 percent of Christians worldwide live as minorities.