“In contrast with [the] baby boom among Muslims, people who do not identify with any religion are experiencing a much different trend,” said Pew. Religiously unaffiliated people make up 16% of the global population, but only produce 10% of the world’s babies.
“This dearth of newborns among the unaffiliated helps explain why religious ‘nones’ (including people who identify as atheist or agnostic, as well as those who have no particular religion) are projected to decline as a share of the world’s population in the coming decades.”
By 2055-2060, 9% of all babies will be born to religiously unaffiliated women, while more than 70% will be born to either Muslims (36%) or Christians (35%), said Pew.
Religiously unaffiliated people are “heavily concentrated in places with ageing populations and low fertility, such as China, Japan, Europe and North America. By contrast, religions with many adherents in developing countries – where birthrates are high and infant mortality rates have been falling – are likely to grow quickly. Much of the worldwide growth of Islam and Christianity, for example, is expected to take place in sub-Saharan Africa,” said Pew.
In 2015, of the world’s 7.3bn people, Christians were the largest religious group, at 31%. Muslims were second at 24%, followed by religious “nones” (16%), Hindus (15%) and Buddhists (7%). Jews, adherents of folk religions (faiths associated with a particular group of people, ethnicity or tribe), and followers of other religions made up smaller shares of the global population.
The projections did not assume that all babies would retain the religion of their parents, but attempted to take religious switching into account, although “conversion patterns are complex and varied”, said Pew.