Religion in flux: Islam surges, Christianity shrinks; Hinduism holds steady

Time of India

10-06-2025

Between 2010 and 2020, the world's population expanded-and so did nearly every major religious group-according to an analysis of over 2,700 censuses and surveys, a Pew Research Center report said.
Christians remained the largest religious group, rising from 2.18 billion to 2.30 billion (+122 million), but their share of the global population shrank from roughly 30.6% to 28.8% (‑1.8 points). Muslims, meanwhile, surged ahead: adding 347 million adherents-the fastest increase among all groups-pushing their total to approximately 2 billion and boosting their global share by 1.8 points to 25.6%, the Pew report said.
Other faith categories saw varied trends: the religiously unaffiliated grew to comprise 24.2% of the world's population (up from 23.3%), while Hinduism and Judaism held steady relative to global population growth.
Buddhists were the only major religious group that had fewer people in 2020 than a decade earlier.
Pew Research Center report on religion
Why it matters: Shrinking Christian share, expanding Muslim & 'Nones' sizes
Chris­tianity's slowing share reflects not demographic stagnation, but religious switching. As Conrad Hackett, the lead author of the report, explains: 'Among young adults, for every person around the world who becomes Christian, there are three people who are raised Christian who leave.'
Despite Christians having a demographic edge via fertility, disaffiliation reversed that advantage.
Conversely, the surge in the religiously unaffiliated reflects the same switching pattern: many individuals raised Christian have transitioned into non-affiliation, compensating for the group's demographic disadvantage-its older population and lower fertility.
As of 2020, Christians were a majority in 120 countries and territories, down from 124 a decade earlier. Christians dropped below 50% of the population in the United Kingdom (49%), Australia (47%), France (46%) and Uruguay (44%).
Pew Research Center report on religion
Why these changes? Demographics vs switching
Islam's growth is fueled primarily by demographics: a youthful age-structure (average Muslim age 24 vs non-Muslim 33), higher fertility rates, and comparatively low levels of religious switching.
Demographic drivers
Pew outlines critical demographic influences shaping religious group sizes.
Age structure: Younger populations naturally grow faster due to more people in childbearing years.
Fertility rates: Higher birth rates lead to larger natural population increase.
Mortality rates also play a role, though less emphasized.
Muslims benefit from both a youthful demographic and high fertility; Hindus hover near the global fertility average; Jews lag due to older age profiles. Buddhists, meanwhile, are shrinking from both demographic disadvantages and religious switching.
Religious Switching
Switching-either toward or away from religion-has been a game-changer.
Christians experienced notable losses due to large numbers disaffiliating.
The unaffiliated gained primarily through former Christians leaving religion-a shift powerful enough to overcome biological disadvantages.
Conversion rates are low or negligible for Hindus and Jews, so these groups held steady; Buddhists declined partly due to people de-identifying .
Between the lines: Regional shifts
Sub-Saharan Christianity
A dramatic geographic shift: sub‑Saharan Africa now hosts around 31% of the world's Christians-up from 24.8% in 2010-while Europe's share has declined sharply. The region's high fertility and youth boost Christian numbers, even as disaffiliation wanes in Europe.
In one notable exception, Mozambique saw its Christian proportion rise by 5 percentage points.
Rise of unaffiliated in China, US, Japan
The unaffiliated are most numerous in China (1.3 billion of 1.4 billion), followed by the US (101 million of 331 million) and Japan (73 million of 126 million). Despite many holding personal religious beliefs, only about 10% of Chinese residents formally identify with a specific denomination.
Buddhism's decline
Buddhists were the only major religious group to shrink in absolute numbers-down from 343 million to 324 million-due to low fertility and defections.
Stable Judaism & Hinduism
As per the Pew report, Hindu and Jewish populations roughly tracked global population changes.
Hindus grew in absolute terms by about 126 million to 1.2 billion, maintaining a stable global share of 14.9%.
Jews increased from roughly 13.8 million in 2010 to 14.8 million in 2020-just 0.2% of the world population.
The combined 'other religions' category (eg, Baha'is, Jains, folk traditions) also mirrored global population growth, holding steady at 2.2%.
What's next
Shifting global balance
Christianity's dominance remains absolute, but its share is eroding due to disaffiliation.
Islam continues steady growth and is projected to approach parity with Christianity by mid-21st century.
The unaffiliated segment, though biologically disadvantaged, is rising due to cultural shifts and deconversion trends.
Cultural and political impact
The rise of secularization, particularly in developed nations, may reshape societal norms and policymaking.
Conversely, religiosity in regions like sub-Saharan Africa and parts of Asia could mean continued importance of religious identity in daily life and governance.