Declining Christianity
In 1900, the world population was approximately 1.65 billion, and Christians numbered 558 million, accounting for 34.5% of the global population. Over the following years, the population has grown exponentially. By 2020, it had surpassed 7.8 billion, with Christians accounting for 2.26 billion, or 28.8%.
Although the number of Christians is growing, the overall growth rate has declined significantly.
Tens of millions slip quietly away from the faith. There are no headlines, no alarms—just hearts drifting, lives disconnecting, but the church is not even noticing. Globally, for every one person who becomes a Christian, about 3.1 people leave the faith, with the majority becoming religiously unaffiliated.
According to the Pew Research Center, if current trends hold, Christianity may no longer be the world's largest religion within the next 50 years.
Citation
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Conrad Hackett, Marcin Stonawski, Yunping Tong, Stephanie Kramer, Anne Shi and Dalia Fahmy.
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“Nearly a quarter of the world’s population is religiously unaffiliated.”, “How the Global Religious Landscape Changed From 2010 to 2020, Pew Research Center, May 30, 2025" https://www.pewresearch.org/religion/2025/06/09/how-the-global-religious-landscape-changed-from-2010-to-2020/pr_2025-06-09_global-religious-change_0-03/
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“The Global Religious Landscape," Pew Research Center, December 18, 2012, https://www.pewresearch.org/religion/2012/12/18/global-religious-landscape-exec/
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“Projected Cumulative Change Due to Religious Switching, 2010-2050", “The Future of World Religions: Population Growth Projection 2010-2050”, April 2, 2015, Pew Research Center, https://www.pewresearch.org/religion/2015/04/02/religious-projections-2010-2050/
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Statistics and Forecasts for World Religions: 1800-2025, January 2015, Gordon-Conwell Theological Seminary. https://www.researchgate.net/publication/308361629_Status_of_Global_Christianity_2015_in_the_Context_of_1900-2050
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The Future of World Religions: Population Growth Projections, 2010-2050, April 2, 2015, https://www.pewresearch.org/religion/2015/04/02/religious-projections-2010-2050/
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The World’s Religions in Figures: An Introduction to International Religious Demography. Todd M. Johnson and Brian J. Grim.