According to the Religion and Public Life Project at the Pew Research Center, there are 2.18 billion Christians worldwide, which is about 31.6 percent of the world population of 6.9 billion, as of 2010. About 50.1 percent of the total are Catholic, 36.7 percent Protestant and 11.9 percent Orthodox.
Although in the past 100 years the overall quantity of Christians has almost quadrupled, the percentage of Christians has remained roughly the same. However, there has been a demographic shift in the number of Christians from Europe and the Americas to the Asia-Pacific region and sub-Saharan Africa. Whereas in 1910, 93 percent of Christians lived in Europe and North and South America, in 2010 the figure was only 63 percent.
The country with the largest Christian population in 2010 is the United States with 246,780,000 Christians, which is 79.5 percent of its population and 11.3 percent of the world's population of Christians. The countries ranking next in total number of Christians are Brazil, Mexico, Russia and the Philippines. The countries with the largest proportions of Christian populations are Vatican City and the Pitcairn Islands with 100 percent, followed by Samoa and Romania with 99 percent.
Christianity has by far the largest percentage of adherents of any religion on Earth. It is followed by Islam, with 1.6 billion, or 23.4 percent of the world's population as of 2010.