Is Islam Fastest Growing Religion In The World?

How the Global Religious Landscape Shifted from 2010 to 2020: A Critical and Expansive Analysis

The decade between 2010 and 2020 saw significant shifts in the global religious landscape. The Pew Research Center, in its landmark 2025 report, analyzed data from over 2,700 censuses, surveys, and population registers to present how the world’s faith affiliations evolved. The changes were shaped not only by raw population growth but also by differing fertility rates, age structures, migration, and patterns of religious switching. This article synthesizes Pew’s findings and adds important context, especially where sociopolitical constraints might affect religious reporting.

The Backdrop: A Growing Global Population

From 2010 to 2020, the world’s population surged, and so did the number of adherents to almost all major religions. Yet, while many religious groups increased in absolute numbers, their relative share in the global population often shifted downward or upward depending on their internal demographic dynamics.

Christianity: Still the Largest, but Losing Share

Christianity remained the largest religious group globally, growing from approximately 2.18 billion to 2.3 billion. However, this 122 million increase did not keep pace with global population growth. As a result, Christianity’s share declined from 30.6% in 2010 to 28.8% in 2020.

Key reasons:

  • High disaffiliation rates, particularly in Europe and North America, where increasing numbers of young people are leaving the religion.
  • Net losses: For every new convert to Christianity worldwide, approximately three people raised as Christians chose to leave the faith.
  • Geographic shift: Sub-Saharan Africa became the region with the largest share of Christians (~31% in 2020), overtaking Europe. This reflects higher fertility and religious retention rates in African nations.

Islam: The Fastest Growing Religion

Islam experienced the largest absolute and proportional growth of any major religion. From 2010 to 2020, Muslims increased by approximately 347 million, reaching around 2 billion followers. Their global share rose from 23.8% to 25.6%.

Contributing factors:

  • Younger median age: Muslims had a global median age of 24 years, compared to 33 years for non-Muslims.
  • High fertility: Muslim women had an average of 2.9 children, significantly higher than the global average.
  • Low disaffiliation: Survey data indicated Muslims left their faith at far lower rates than Christians or unaffiliated individuals.

However, this last point deserves a closer and more critical look.

A Cautionary Note on Muslim Disaffiliation

While Pew’s data indicates low disaffiliation among Muslims, this statistic must be interpreted cautiously. In many Muslim-majority countries, apostasy (leaving Islam) is not just frowned upon—it is criminalized and in some cases, punishable by death. Countries such as Saudi Arabia, Iran, Afghanistan, and Pakistan enforce harsh penalties for leaving Islam.

Even where the state does not prosecute apostasy, social stigma, ostracization, and threats of violence are common. As a result, many people who no longer believe in Islam may still identify as Muslim in public surveys out of fear for their safety or acceptance.

This creates a “chilling effect” in surveys:

  • Individuals might misreport their true beliefs.
  • They may continue to identify as Muslim for legal or social protection.
  • Surveys in such regions cannot capture the full spectrum of private belief.

Online, however, there is growing evidence of hidden disaffiliation. Ex-Muslim communities on platforms like Reddit, YouTube, and X (formerly Twitter) have grown significantly, offering a glimpse into a silent movement of people who have left the faith but cannot do so openly.

Prominent voices like Ayaan Hirsi Ali, Yasmine Mohammed, and Harris Sultan have all documented this trend, especially among youth in the Middle East, South Asia, and the diaspora. Therefore, while Islam appears to have strong retention, the reality may be far more complex and nuanced than survey data suggests.

The Religiously Unaffiliated: Rising, but Facing Demographic Constraints

The religiously unaffiliated category includes atheists, agnostics, and those who describe their religion as “nothing in particular.” This group grew from 23.3% to 24.2% of the global population.

Trends shaping their growth:

  • Losses from Christianity were the primary driver, especially in the West.
  • Youth-led disaffiliation has accelerated in countries with religious freedom.
  • However, lower fertility rates and older age structures have limited their demographic growth, despite rising cultural prominence.

Hinduism: A Steady Pillar Amidst Global Flux

Hinduism, the world’s third-largest religion, remained relatively stable in its global share during the 2010 to 2020 decade. The total number of Hindus rose in absolute terms, driven largely by India’s large and youthful population. Despite this growth, the overall global percentage of Hindus did not see a dramatic rise or fall, hovering around 15%. What sets Hinduism apart is its strong regional concentration—primarily in India and Nepal—with small but growing diasporic communities in countries such as the United States, the United Kingdom, Canada, and the Caribbean.

Fertility among Hindus remained close to global averages, but the religion exhibited remarkable internal cohesion, with relatively low levels of disaffiliation and conversion. Hinduism also faced fewer losses from religious switching compared to Christianity. Cultural continuity, intergenerational traditions, and integration of spiritual practices into daily life contributed to its resilience. However, rising secularism among some urban youth and increasing interaction with global ideologies have posed soft challenges to traditional beliefs. Nonetheless, Hinduism continues to maintain its foundational strength as a civilizational tradition rather than a strictly institutionalized faith system.

Other Faiths: Diverse Trends

  • Buddhism: Declined slightly from 343 million to 324 million, attributed to low fertility and higher disaffiliation in some regions.
  • Judaism: Stayed numerically stable, with modest demographic shifts mostly concentrated in the U.S. and Israel.
  • Folk and traditional religions: Generally localized and stable, though under pressure from modernization and religious competition.

The Role of Age and Fertility

Demographic factors heavily influenced religious growth:

  • Muslims and Christians were the youngest and had the highest fertility rates.
  • Buddhists and unaffiliated populations had below-replacement fertility levels.

These trends suggest that, purely based on demographics, Islam and Christianity will continue to grow, while groups like Buddhists and the unaffiliated may face future demographic stagnation.

Religious Switching: A Powerful Driver

Religious switching (changing one’s religious identity) is among the most important but under-discussed forces reshaping the religious landscape:

  • Christianity saw a net loss of 8 million due to switching between 2015 and 2020.
  • The religiously unaffiliated gained around 7.6 million due to switching, mostly from Christianity.
  • Islam and Hinduism saw relatively smaller net changes from religious switching.

In countries like the U.S., U.K., and parts of Western Europe, switching has led to visible declines in church attendance and affiliation among younger generations.

Regional Shifts: Faith on the Move

Religious identity is not evenly distributed. Geographic patterns show marked changes:

  • Sub-Saharan Africa became the new center of gravity for Christianity.
  • The Middle East and Asia-Pacific retained their prominence in the Muslim world.
  • The unaffiliated remained concentrated in East Asia and the West.
  • Europe and North America saw overall religious decline, while Africa and South Asia saw religious growth.

By 2060, projections indicate that 42% of Christians and nearly 27% of Muslims may live in Sub-Saharan Africa, signaling a profound shift in where religious authority and cultural expression may lie.

Looking Ahead: 21st-Century Religion

Pew Research and other demographers suggest that by mid-century:

  • Islam may surpass Christianity in global numbers.
  • Africa will be the spiritual heartland of both Christianity and Islam.
  • Secularization will accelerate in advanced economies but slow elsewhere.
  • Religious nationalism, migration, and political identity may further complicate the picture.

Final Thoughts

The global religious landscape is changing, but not uniformly. Christianity and Islam remain dominant but face different challenges: disaffiliation for Christianity, and suppressed dissent within Islam. The religiously unaffiliated are growing in influence but face demographic stagnation. Hinduism, meanwhile, remains a stable and cohesive civilizational force.

What becomes clear is that religious identity is increasingly shaped by freedom, fertility, and fear. Where people are free, they may leave religion; where they are young and growing, religion spreads; and where they are afraid, surveys may not tell the truth.

These nuances remind us that behind every statistic is a story—of belief, doubt, silence, and sometimes, quiet rebellion.

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