How Religious Composition Around the World Differs between Younger and Older Populations

Abstract

This graphic shows differences in the religious composition of people around the world by age group. Religious change caused by demographic processes is more than a hypothetical future possibility. The consequences of demographic differences can be seen today by comparing the religious composition of younger and older populations.

Demography is transforming the world’s religious makeup (Hackett, Connor, et al. 2015). Muslims, for example, have the highest total fertility rate among major religious groups (2.9 children per woman), fueling projections that their number will increase 70 percent between 2015 and 2060, which is more than twice the amount of growth expected (32 percent) among the general population (Hackett, Stonawski, and McClendon 2017).

While population projections model expected future change, skeptics rightly note that we should be humble about anticipating the future given all the ways it may surprise us. Yet without waiting for a distant future, we can see the impact of demography on religious populations by comparing the religious composition of younger and older populations (Figure 1).

Figure 1.

Estimated percentage of world’s population in each religion category, by age group (2015).

Due to past differences in fertility and mortality rates, there are some notable present differences in the global religious composition of age groups. Among those ages 40 and older, Muslims are estimated to be 17 percent of the 2015 population, the third largest religious category among this older group. But Muslims account for 28 percent of children and adults under the age of 40, making them the second largest group among younger people. Similarly, Hindus make up 13 percent of the older group and a larger share, 16 percent, of the younger population.

The opposite pattern emerges for the religiously unaffiliated—those who describe themselves as atheists, agnostics or “nothing in particular.” Also known as nones, these people make up the second largest group among those ages 40 and older (20 percent), primarily because of their high concentration among the relatively old populations of East Asia (Hackett et al. 2017). However, they remain relatively scarce among the burgeoning young populations of Africa and South Asia—and even their rapid growth among the young populations of the United States and Western Europe isn’t enough to counter the even faster growth of Muslims, Hindus, and Christians in high-fertility regions (Hackett, Stonawski, et al. 2015). Consequently, the unaffiliated make up only 14 percent of people worldwide under 40.

Christians continue to be and are projected to remain the world’s largest religious group despite the lower incidence of Christians among those under age 40 (30 percent vs. 33 percent). This is tied to a significant geographic shift that is underway: In recent centuries, Christians have been heavily concentrated in Europe, but their numbers in this aging region are now declining as deaths of European Christians outnumber births (Hackett et al. 2017). Increasingly, Christians are becoming concentrated in sub-Saharan Africa, a young and fertile region where their number is expected to continue growing dramatically in the decades to come (McClendon 2017).

Buddhists are less common among the under-40 crowd (6 percent) compared with their elders (9 percent). Buddhists are not having enough children to sustain their global population share, and unlike the religiously unaffiliated, religious switching is not expected to increase Buddhist numbers in future decades (Hackett et al. 2017; Skirbekk et al. 2015).

Supplemental Material

SRD854943_Supplemental_material_CLN – Supplemental material for How Religious Composition Around the World Differs between Younger and Older Populations

Supplemental material, SRD854943_Supplemental_material_CLN for How Religious Composition Around the World Differs between Younger and Older Populations by Conrad Hackett in Socius