Islam is growing faster than any other religion on Earth, according to a new study from the Pew Research Center.

Muslims now make up 25.6% of the world’s population, second to Christianity’s 28.8%. But while Christianity grew in raw numbers its global share slipped somewhat, weighed down by aging populations, lower fertility and millions of people leaving the faith altogether.

The sweeping report, released Monday, shows that Muslims saw the sharpest growth of any religious group between 2010 and 2020. Researchers said the reason for the nearly 2% growth likely lies with Islam’s youthful population and high birthrates, not conversions.

Muslim writer Sayed M. Mahdi Al-Modarresi, in an op-ed for Al-Islam TV, wrote that Islam’s “religious scriptures are clear as daylight that Islam wants us to have as many children as possible.”

“I reiterate: as many children as possible, meaning that you should not set a cap on the number of kids you are going to have,” Mr. Al-Modarresi wrote. “Which is one of the conversations that people bring up when they are getting to know each other, even before they get married, perhaps, right?”

The study analyzed more than 2,700 censuses and surveys across 201 countries and territories, covering nearly the entire global population.

Christianity is still the world’s largest religion — and the majority in most regions. Even so, it’s losing ground (it was at 30.6 in 2010). Sub-Saharan Africa, too, now has more Christians than Europe.

At the same time, large numbers of former Christians are swelling the ranks of the religiously unaffiliated.

The so-called “nones” (atheists, agnostics and people who simply say they have no religion) also saw their share climb, making them the third-largest religious category globally at 24.2%. That’s up from 16% a decade ago.

While Islam and the “nones” gained ground, Buddhism shrank.

Buddhists were the only major group to decline in total numbers, dropping to 4.1% of the population. Pew cites a low birthrate and rising disaffiliation in East Asia for the slide.

Hinduism held steady at 14.9%, with nearly all living in the Asia-Pacific region and 95% in India alone.

Meanwhile, Jews, at just 0.2% of the global population, also fell behind the world’s growth rate, thanks to an older average age profile. Most Jews, says Pew, live in North America and Israel.

The new findings for the Pew Center are part of the organization’s Global Religious Futures project.

• Emma Ayers can be reached at eayers@washingtontimes.com.