Christian share of global population shrinks

Muslims are the fastest-growing religious group

By Leonardo Blair, Senior Reporter Thursday, June 12, 2025

A new Pew Research Center report shows that although Christianity continues to be the world’s largest religious group, its share of the rising global population has fallen over the last decade, mainly due to people walking away from the faith.

The report, based on an analysis of 2,700 censuses and surveys, shows that the global population of Christians grew by 121.6 million people from 2010 to 2020, reaching some 2.3 billion people. As a share of the global population, estimated to be about 7.8 billion in 2020, Christians fell by 1.8 percentage points to 28.8%.

The global population of Muslims, on the other hand, reached 2 billion, registering an increase of 347 million. Their share of the global population increased by 1.8 percentage points to 25.6%. The study also recognized Muslims as the world’s fastest-growing religious group.

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The biggest driver of the decline in the share of Christians in the global population was religious disaffiliation, researchers noted. They found that even though more people grew up with a religious affiliation than those who didn’t when it comes to Christianity, more people who grew up with the faith have begun identifying as religiously unaffiliated than unaffiliated people who now identify with the religion.

The religiously unaffiliated, according to Pew Research, are people who identify as atheist, agnostic or “nothing in particular.”

“Religious disaffiliation is the main driver of the decline in the Christian share of the global population. Religious disaffiliation — primarily of people leaving Christianity — also is the main driver of the growth of religiously unaffiliated populations,” the researchers noted.

Individuals around the world identifying as religiously unaffiliated grew by 270.1 million between 2010 and 2020 to reach a total of 1.9 billion. They represent nearly a quarter of the world’s population or 24.2%

To better understand the issue of religious disaffiliation and religious switching, the researchers examined surveys from 117 countries.

“To capture switching that has occurred in more recent years, we use data from adults ages 18 to 54. Religious switching is more common earlier in life, though it can happen at any age,” they noted.

“We found that for every adult in that age group who says they joined a religion after having been raised without a religion, 3.2 moved in the other direction — they left religion altogether after having been raised in one,” they explained. “As a result, based on this set of measures, the religiously unaffiliated category has had the largest net gain due to switching.”

And the inverse was true for Christianity.

“Christians have experienced the biggest net losses from switching (3.1 have left for every 1.0 who has joined). Most former Christians no longer identify with any religion, but some now identify with a different religion,” researchers noted.

As of 2020, China led the world with the most religiously unaffiliated people. Some 90% of that country’s population, or 1.3 billion people, identified as religiously unaffiliated.

America followed in second place with approximately 101 million people identifying as religiously unaffiliated in 2020, reflecting a 97% increase from a decade earlier.

It was also noted that sub-Saharan Africa is now home to the largest number of Christians, surpassing Europe. In 2020, 30.7% of the world’s Christians lived in sub-Saharan Africa, while only 22.3% lived in Europe.

While most countries, some 120, still remained Christian-majority countries, the study showed that religious disaffiliation has been slowly changing the religious landscape.

The Christian population dropped below 50% in the United Kingdom (49%), Australia (47%), France (46%) and Uruguay (44%), the report noted.

“In each of these places, religiously unaffiliated people now account for 40% or more of the population, and smaller religious groups such as Muslims, Hindus, Buddhists, Jews or adherents of other religions (combined) account for 11% or less,” researchers said.

Over the period of the analysis, religiously unaffiliated people became a majority in the Netherlands (54%), Uruguay (52%) and New Zealand (51%.) They joined China, North Korea, the Czech Republic, Hong Kong, Vietnam, Macao and Japan, which had religiously unaffiliated majorities in 2010, the report said.

In 2022, a Pew study found that barring any limiting event such as war or economic depression, if the pace at which Christians abandon their faith before the age of 30 were to accelerate beyond its current pace, America could no longer be a majority Christian nation by as early as 2045.

“Of course, it is possible that events outside the study’s model — such as war, economic depression, climate crisis, changing immigration patterns or religious innovations — could reverse current religious switching trends, leading to a revival of Christianity in the United States,” the researchers noted. “But there are no current switching patterns in the U.S. that can be factored into the mathematical models to project such a result.”