A Decade of Growth: How Christianity Outpaced Islam from 2015 to 2025

Between 2015 and 2025, global religious demographics shifted in ways that challenge the prevailing narrative that Islam is the world’s fastest-growing faith. While Muslims continued to expand steadily, the data shows that Christians experienced a larger absolute increase in population over the decade—driven primarily by rapid growth in sub-Saharan Africa, parts of Asia, and the continuing demographic weight of the Americas.

The Numbers at a Glance

• Christians
  2015: ~2.24 billion
  2025: ~2.60 billion
  Increase: ~360 million (+16%)

• Muslims
  2015: ~1.77 billion
  2025: ~2.00 billion
  Increase: ~230 million (+13%)

The difference is striking: Christians added roughly 130 million more people than Muslims over the decade, reversing the narrower growth gap observed in the previous period (2005–2015).

Why Christian Growth Surpassed Muslim Growth

1. Africa’s demographic surge
   Africa became the decisive factor. Christian populations in Nigeria, the Democratic Republic of the Congo, Ethiopia, Tanzania, and Uganda posted double-digit percentage increases, adding tens of millions each. Sub-Saharan Africa now houses the largest regional concentration of Christians, having overtaken Europe by 2020 and continuing to widen that lead into 2025.

2. High retention in the Global South
   While the West saw continued secularization, Christian communities in Africa, Latin America, and parts of Asia retained high adherence rates alongside strong fertility, keeping growth robust.

3. Steady gains in Asia-Pacific
   The Philippines, South Korea, and smaller Pacific nations added to the Christian total, while conversion movements in China and Southeast Asia—though often underreported—contributed incrementally.

4. Latin America’s momentum
   Brazil and Mexico, two of the world’s largest Christian-majority nations, expanded in absolute numbers despite internal shifts from Catholicism to evangelical and Pentecostal movements.

What Could Explain the Slower Growth in Muslims

Although Islam remains one of the fastest-growing religions globally, several factors contributed to its slower growth relative to Christianity over the 2015–2025 period:

1. Declining fertility in key Muslim-majority countries
   Nations such as Iran, Turkey, Indonesia, and parts of North Africa experienced sharp drops in fertility rates, in some cases falling below the global average. This slowed natural population growth in regions that had historically driven Muslim expansion.

2. Demographic maturity in the Middle East
   Many Middle Eastern countries have aging populations compared to the past, and while still youthful by global standards, their growth rates are tapering as urbanization and education levels rise.

3. Regional conflicts and instability
   Prolonged conflicts in Syria, Yemen, and parts of the Sahel have caused significant displacement, reduced access to healthcare, and increased mortality—factors that can hinder long-term population growth.

4. Minority status in high-growth regions
   In countries with the highest population growth—such as much of sub-Saharan Africa—Christians make up a larger share of the population, so the majority of demographic momentum in those regions benefits Christianity.

5. Migration patterns
   While migration to Europe and North America has boosted Muslim populations, these gains were not large enough to offset the slower natural growth in core Muslim-majority nations.

The Strategic Implications

• Christianity’s center of gravity is now firmly anchored in the Global South, where growth shows no signs of slowing and where the youthful demographic profile will shape global Christian influence for decades.

• Islam’s growth remains strong but is no longer outpacing Christianity in absolute terms—shifting the long-term forecast for when (or if) the two populations converge.

• Policymakers, faith leaders, and NGOs must recalibrate strategies to address the reality that Africa is emerging as the epicenter of both religions, with the potential for increased interfaith interaction and competition.

Bottom line:
The decade from 2015 to 2025 marks a turning point—Christianity not only maintained its lead as the world’s largest religion but widened the numerical gap over Islam. While both faiths continue to grow, the African demographic engine has propelled Christians into a position of renewed global numerical dominance.

References

Center for the Study of Global Christianity. (2025). Status of global Christianity, 2025, in the context of 1900–2050. Gordon-Conwell Theological Seminary.

Pew Research Center. (2025). How the global religious landscape changed from 2010 to 2020. Washington, DC: Pew Research Center.

Pew Research Center. (2015). The future of world religions: Population growth projections, 2010–2050. Washington, DC: Pew Research Center.

Pew Research Center. (2011). Global Christianity: A report on the size and distribution of the world’s Christian population. Washington, DC: Pew Research Center.

United Nations, Department of Economic and Social Affairs, Population Division. (2024). World population prospects 2024. United Nations.