While the global population is expected to grow 32 percent by 2060, the number of Muslims is expected to grow 70 percent, according to the Pew Research Center. In the second half of this century, the number of Muslims is projected to surpass the number of Christians around the world.

Conrad Hackett (@conradhackett), associate director of research and senior demographer at Pew Research Center, joins Here & Now's Jeremy Hobson with more on what's behind the growth.

Interview Highlights

On why the global Muslim population is growing so rapidly

"Muslims are the youngest major religious group in the world. They have a median age of 24. And Muslims have more children than people in any other group. About three children per woman who's Muslim, compared to about 2.2 children per woman who's not Muslim in the world."

"People of course do change religious faiths, and we've measured religious switching, but for Muslims the story as far as we can tell is really about natural increase: a lot more Muslims being born than are dying in any given year."

On people changing their religious identity

"We've studied a couple dozen Muslim-majority countries, and we don't see much change in religious identity in those countries. In Egypt, for example, most people who grew up Christian retain that identity as adults, and the same for those who grew up Muslim. There are some restrictions on switching faith in Muslim-majority countries. You might be stigmatized or face legal consequences for apostasy for changing faith. So that's a factor that they limit what we can capture. But the big change in terms of religious switching in the world is from people who grew up Christian to those who now identify with no religion. And that population of people who claim no religion is growing a lot through religious switching, not through fertility. Those folks tend to have fewer children than people who have a religious affiliation."