The phrase “spiritual but not religious” has become widely used in recent years by some Americans who are trying to describe their religious identity. While Pew Research Center does not categorize survey respondents in such a way, our surveys do find that the U.S. public overall appears to be growing a bit less religious – but also somewhat more spiritual.
As of 2010, Christianity was by far the world’s largest religion, with an estimated 2.2 billion adherents, nearly a third (31%) of all 6.9 billion people on Earth. Islam was second, with 1.6 billion adherents, or 23% of the global population. If current demographic trends continue, however, Islam will nearly catch up by the middle of the 21st century. Between 2010 and 2050, the world’s total population is expected to rise to 9.3 billion, a 35% increase, reports the Pew Forum on Religion.