How long will it stay #1?
A recent report from the Pew Research Center reveals that while Christianity remains the most widely followed religion globally, its share of the total population has declined over the past decade—largely due to increasing numbers of people leaving the faith.
Analyzing data from 2,700 global surveys and censuses, the report shows that the Christian population rose by over 121 million between 2010 and 2020, reaching approximately 2.3 billion. However, as a proportion of the world’s population—estimated at 7.8 billion in 2020—Christianity’s share dropped by 1.8 percentage points, settling at 28.8%.
In contrast, the Muslim population grew by 347 million during the same period, reaching 2 billion. Their global share rose to 25.6%, making Islam the fastest-growing major religion, according to the study.
A key factor in the relative decline of Christianity’s global share is religious disaffiliation. The report finds that more people who were raised Christian have stopped identifying with any religion than people without a religious upbringing who later converted to Christianity.
Those categorized as religiously unaffiliated—including atheists, agnostics, and individuals identifying with no particular faith—grew by 270 million in the decade, totaling 1.9 billion or 24.2% of the global population.
To explore trends in disaffiliation and religious switching, Pew examined data from 117 countries, focusing on adults aged 18 to 54, the age range when people are most likely to change their religious identity. For every one person in that age group who adopted a religion after being raised without one, more than three left religion after being raised in it.
Christianity experienced the most significant losses due to switching. For every person who converted to Christianity, roughly 3.1 people left it. Most of these individuals became religiously unaffiliated, while a smaller number joined other faiths.
China had the highest number of religiously unaffiliated individuals in 2020, with about 90% of its 1.3 billion population not identifying with any religion. The United States ranked second, with around 101 million unaffiliated individuals—nearly double the figure from 2010.
The study also highlights that sub-Saharan Africa has surpassed Europe as the region with the largest Christian population. In 2020, over 30% of Christians lived in sub-Saharan Africa, compared to 22.3% in Europe.
While Christianity still dominates in about 120 countries, the shift toward disaffiliation is gradually reshaping global religious demographics. For example, Christian populations fell below 50% in the United Kingdom (49%), Australia (47%), France (46%), and Uruguay (44%), where unaffiliated individuals now make up at least 40% of the population.
Some countries—including the Netherlands (54%), Uruguay (52%), and New Zealand (51%)—have joined places like China, Japan, and the Czech Republic as majority unaffiliated nations.
A 2022 Pew projection warned that if current trends continue, and disaffiliation among younger Americans accelerates, Christianity may no longer be the majority religion in the U.S. by 2045. While unforeseen events—like wars, economic crises, or religious revivals—could alter this trajectory, the current data show no such reversal in sight.