Christians are projected to remain the world’s largest body of believers for 40 years, but the fast-growing Muslim population is likely to close the gap after 2050, says a first-of-its-kind report released Thursday by Pew Research Center.
The report — based on six years of research — suggests that, except for Buddhism, the world’s major religions are expected to grow in the next four decades.
The religious composition of many countries is also likely to shift: America, for instance, will become less Christian; Europe will become more Muslim; and India will maintain a Hindu majority, but replace Indonesia as home to the world’s largest Muslim population.
Eight groups — including atheists and other nonbelievers — are analyzed in the report, with details about virtually all regions and nations in the world.
“I think there’s something here for everybody,” demographer and lead author Conrad Hackett said Wednesday.
The 245-page report was conducted as part of the Pew-Templeton Global Religious Futures Project.
It estimates that Christian believers will grow in membership from 2.2 billion in 2010 to 2.9 billion in 2050.
However, they will remain at about 31 percent as a share of the world population, said the report. That’s because the growth of Christian membership will be about the same as the overall growth in the world population, from 6.9 billion in 2010 to around 9.3 billion in 2050.
Muslims — who have comparatively youthful populations — are expected to dramatically grow in numbers, from 1.6 billion to 2.8 billion. As a result, their share of the world’s population is expected to swell from 23 percent to almost 30 percent over 40 years.
Hindus will also multiply, from 1 billion in 2010 to 1.4 billion in 2050, but remain stable at about 15 percent of the world’s population.
Jews, who numbered about 14 million in 2010, will rise to 16 million and continue to represent 0.2 percent of the world population.
In contrast, the number of Buddhists is projected to stay stable, with around 487 million adherents over the next 40 years. However, due to the faith’s popularity in countries with low-fertility rates and aging populations, their representation in the world will shrink from 7 percent to 5 percent, said the study.
The report also includes categories called “folk religions” and “other religions” to capture people who adhere to native, traditional rituals, as well as those who practice Taoism, Shintoism, Baha’i, Jainism and Sikhism.
Both “folk” and “other” categories are expected to see growth in numbers, but not in their share of the world population.
The 1.1 billion atheists, agnostics and other “unaffiliated” people face a mixed future, according to the report.
The number of these nonbelievers may increase by 100 million over 40 years, with strongholds in places such as the United States and Europe, but their share of the global population is expected to wane from 16 percent to 13 percent.
The report didn’t break down religious populations into subgroups, which means the Muslim category includes Sunni and Shia, while the Christian category includes Catholics, Protestants, Orthodox, Mormons, Jehovah’s Witnesses and Christian Scientists.
The report looked at five things as key factors driving their global projections. These included fertility and childbearing decisions; life expectancies; international migration; the size of the youth population in a nation or region; and “religious switching” — when people acquire, depart or change their faith.
Tracking people’s faith identity over their lifespan “is something that is pretty new, in terms of demographic modeling,” Mr. Hackett said. “It’s been done at the country level, but never at the global level” until this report, he said.