Islam, the world’s fastest-growing faith, will leap from 1.6 billion (in 2010) to 2.76 billion by 2050, according to the Pew study. At that time, Muslims will make up nearly one-third of the world’s total projected population of about 9 billion people.
Christianity is expected to grow, too, but not at Islam’s explosive rate. The Pew study predicts Christians will increase from 2.17 billion to 2.92 billion, composing more than 31% of the world’s population.
This means that by 2050, more than 6 out of 10 people on Earth will be Christian or Muslim. And, for perhaps the first time in history, Islam and Christianity would boast roughly equal numbers.
Looking even farther into the future, Islam’s population could surpass Christianity by 2100, Pew says, despite Christians’ six-century head start. (It’s possible that Muslims outnumbered Christians sometime in the past, perhaps during the Black Plague that decimated Europe. But scholars aren’t certain.)
Based in Washington, Pew is a nonpartisan “fact tank” that regularly produces sweeping surveys of this kind without taking public policy positions.
The study, which Pew says is the first of its kind, bases its projections on the age of populations, fertility and mortality rates, as well as migration and conversion patterns. Simply put, Muslims are having larger families, retaining more members (conversions are illegal in some Muslim nations) and are younger than adherents of other faiths. More than 1 in 3 Muslims is younger than 15.