The population of the Abrahamic religions

How many people belong to each Abrahamic tradition, and how is that changing? The most detailed answer comes from the Pew Research Center, which in 2015 published the first large-scale demographic projections of the world’s religions, built from more than 2,500 censuses, surveys and population registers rather than estimation alone.¹

The present picture

As of Pew’s baseline year, Christians were the largest religious group in the world, with Muslims second.² Jews were, and remain, by far the smallest group for which Pew produced a separate projection, numbering a little under 14 million worldwide, some 0.2 per cent of the global population.³ Mandaeism, with a global community numbered in the tens of thousands, falls beneath the threshold at which census and survey data allow a demographer to project it separately at all; it appears in no study of this kind, Pew’s included.

What drives the difference

Pew traces future change mainly to fertility and age, not conversion. Globally, Muslim women have the highest fertility of any major religious group, an average of 3.1 children, against 2.7 for Christians and 2.3 for Jews, all above the replacement level of 2.1.⁴ Muslims also have the youngest median age of any group Pew measured, seven years below the median for non-Muslims, which means a larger share of Muslims are approaching the years in which people have children.⁵ Both patterns concentrate in sub-Saharan Africa and parts of Asia, where Muslim and Christian populations are both growing quickly, while the regions where the religiously unaffiliated are concentrated, Europe, North America, China and Japan, have low fertility and ageing populations.⁶

The projection to 2050 and 2060

On these trends, Pew’s central projection has Christians and Muslims reaching near parity by 2050, at 2.9 billion (31 per cent of the world’s population) and 2.8 billion (30 per cent) respectively, the first time in history the two would stand so close.⁷ A later Pew analysis, extending the same model to 2060, projects that Muslims would overtake Christians as the world’s largest religious group in the second half of the century, growing 70 per cent between 2015 and 2060 against 32 per cent for the world’s population as a whole.⁸ The Jewish population is projected to keep growing in absolute terms, to about 16.1 million by 2050, while continuing to decline slightly as a share of the world’s much faster-growing population.⁹

Where Christians will live

The same projections show Christianity shifting its centre of gravity. In 2010 the world’s Christians were spread almost evenly across Europe (26 per cent), Latin America and the Caribbean (25 per cent) and sub-Saharan Africa (24 per cent), while fewer than 1 per cent lived in the Middle East and North Africa, the region where the faith began. By 2050 Pew projects that 38 per cent of the world’s Christians will live in sub-Saharan Africa and only about 16 per cent in Europe, the one region where the number of Christians is expected to fall in absolute terms, from 553 million to 454 million.¹⁰ Nigeria is projected to hold the world’s third-largest Christian population by mid-century, although Christians would then make up only 39 per cent of its people.¹¹

Conversion plays a modest part worldwide and a larger one in the West. Pew projects net losses to Christianity through religious switching in North America, Europe and Latin America, most of it toward no religious affiliation: without switching, Christians would make up about 75 per cent of North America’s population in 2050, against 66 per cent once switching is counted. In sub-Saharan Africa, where the number of Christians is expected to more than double, their share of the population is still projected to slip from 63 to 59 per cent, because the region’s Muslim population is growing faster still.¹²

A historical footnote

Pew’s researchers also asked historians when Christians and Muslims were last so close in number. Most hold that Christians have always outnumbered Muslims worldwide since Islam’s rise in the seventh century, given Christianity’s six-century head start. A minority view, associated with the Oxford demographer David Coleman and the Columbia historian Richard Bulliet, holds that Muslims may briefly have outnumbered Christians sometime between 1000 and 1600 CE, as Muslim populations expanded while plague, above all the Black Death, cut deeply into Europe’s Christian population. Pew is careful to note that estimates for this period carry wide uncertainty.¹³

What a projection is not

None of this is a prophecy. Pew’s own report says plainly that the projections describe what would follow if current fertility, mortality, migration and conversion patterns continue, and that events ranging from conflict to economic change can move demographic trends in ways no model can foresee; this is why the projections cover a bounded forty- to forty-five-year window rather than reaching further into the century.¹⁴ Read that way, the figures describe a trajectory worth understanding on its own terms, not a settled outcome. See Islam and Christianity.

Notes

1. Conrad Hackett et al., “The Future of World Religions: Population Growth Projections, 2010-2050” (Washington, DC: Pew Research Center, 2 April 2015). ↩
2. Hackett et al., “The Future of World Religions,” Overview. ↩
3. Ibid., ch. 2, “Jews.” ↩
4. Ibid., ch. 1, “Fertility.” ↩
5. Michael Lipka and Conrad Hackett, “Why Muslims Are the World’s Fastest-Growing Religious Group,” Pew Research Center, 6 April 2017 (an update of an article first published 23 April 2015). ↩
6. Hackett et al., “The Future of World Religions,” Overview. ↩
7. Ibid., Overview and ch. 2, “Christians” and “Muslims.” ↩
8. Lipka and Hackett, “Why Muslims Are the World’s Fastest-Growing Religious Group.” ↩
9. Hackett et al., “The Future of World Religions,” ch. 2, “Jews.” ↩
10. Hackett et al., “The Future of World Religions,” ch. 2, “Christians,” “Regional Change.” ↩
11. Ibid., “Change in Countries With Largest Christian Populations.” ↩
12. Ibid., “Regional Change” and “Demographic Characteristics of Christians That Will Shape Their Future.” ↩
13. Ibid., Overview, note 2, citing Todd M. Johnson, Houssain Kettani, David Coleman and Richard W. Bulliet. ↩
14. Ibid., Overview, “Why Do Some Religious Groups Grow Faster Than Others?” ↩