A comprehensive new study by the Pew Research Center has revealed that Muslims are currently the fastest-growing religious group in the world, with the religiously unaffiliated not far behind. While Christianity continues to hold its place as the largest global religion, it has experienced a decline in its overall percentage of the global population between 2010 and 2020.
Released on June 9, the Pew Research Center’s Global Religious Landscape report is the second major demographic overview of religious groups worldwide, following the initial edition in 2010. This latest study draws attention to how factors like fertility, mortality, age distribution, education, and migration have shaped religious growth and decline across continents.
“We look at the demographic characteristics of these groups, their age structure, how many children they’re having, how much education they have, because these demographic characteristics affect the future size of the religious groups,” explained Conrad Hackett, a senior demographer at Pew Research Center, in an interview conducted on June 6.
The research focused on major world religions including Christianity, Islam, Hinduism, Buddhism, Judaism, and the religiously unaffiliated or “nones.” It also considered smaller or traditional groups categorized as “others,” such as folk religions, Wiccans, and Zoroastrians.
The findings offer crucial insights into how religious switching and natural demographic shifts have altered the global religious landscape. According to the report, the Muslim population grew by an astonishing 347 million people over the decade, surpassing the growth of all other religious groups combined. This spike was primarily the result of high birth rates among Muslim populations.
“Muslims are having children at a greater number than Muslims are dying,” Hackett said. “Very little of the change in Muslim population size is a result of people becoming Muslim as adults or leaving Islam as adults.”
To produce the study, Pew researchers analyzed 2,700 data sources, including national censuses, population and demographic surveys, and official registries. These sources represented 201 countries and provided data on over 100,000 people. Questions primarily focused on religious affiliation and were used in conjunction with statistics on fertility, death rates, and age structures to evaluate changes from 2010 to 2020. The study also acknowledged the impact of data delays caused by the COVID-19 pandemic.
Muslims are heavily concentrated in regions experiencing rapid population growth. For instance, in the Middle East and North Africa, they make up 94.2% of the population, while in sub-Saharan Africa, they constitute 33%. The Asia Pacific region, home to the world’s largest Muslim population, experienced a 16.2% rise in its Muslim population during the decade studied.
Christianity, despite remaining the largest religion globally with 29% of the population, saw a 1.8% dip in its global share. The number of Christians grew numerically, but not at the same pace as non-Christian populations. Hackett noted that Christianity witnessed declines in regions such as Europe, North America, the Americas, Australia, and New Zealand.
Europe experienced an 8.8% drop in its Christian population, while North America saw a 10.8% decline. In the United States, Christians dropped from 78.3% of the population to 64% over the course of the study. Other countries like France, Uruguay, the United Kingdom, and Australia also saw the Christian share dip below 50%.
The primary causes for Christianity’s decline in Europe included an aging population, lower birth rates, and higher mortality. Meanwhile, sub-Saharan Africa emerged as a new stronghold for the faith, now hosting one-third of all Christians globally due to higher fertility rates.
Christianity continues to be the majority religion in all global regions except the Middle East-North Africa and Asia Pacific. Despite its relative decline, it remains the most geographically dispersed religious tradition worldwide.
Meanwhile, the population of non-Christians grew by 15%, bolstered significantly by the rising number of religiously unaffiliated individuals. With 24% of the global population now identifying as nones, they rank as the third-largest group after Christians and Muslims.
Although the nones have an older demographic and lower fertility rates, their numbers increased primarily because of religious switching. The study found that for every adult raised without religion who later adopted one, 3.2 adults abandoned the religion in which they were raised.
“This pattern is common in European and North American countries, as well as in Australia and New Zealand, where many people who were raised Christian no longer claim any religious affiliation,” the report stated.
Hackett added, “Christians are seeing a lot of people who are raised in the faith changing as adults to people who don’t identify with any religion.”
This report marks the first time Pew has attempted to track religious switching trends, using data from 117 countries to compare the faiths individuals were born into with the religions they identified with as adults.
In North America, the proportion of religiously unaffiliated grew by 13 percentage points, reaching 30.2% by 2020. The trend was also evident in Latin America-Caribbean, where nones rose by 4.1 percentage points, and in Europe, where they grew by 6.6 percentage points to reach 25.3%.
The Asia Pacific region hosts the largest number of nones, with 78.3% of the world’s religiously unaffiliated population living there. A staggering 67% of them are located in China. However, Hackett acknowledged the difficulty of analyzing religious identity in China, stating that Pew has conducted specific research into the complex dynamics of religiosity in the country.
“China has 7 times as many religiously unaffiliated people as the U.S. and Japan combined,” the report highlighted.
Buddhism, another major religion, saw a net decline during this period. Between 2010 and 2020, the global Buddhist population fell by 19 million due to both disaffiliation and low demographic growth. It was the only major religious group to lose members.
The report noted that the impact of Buddhism may be underrepresented since many individuals practice Buddhist customs without formally identifying as Buddhists.
Hindus, who make up 14.9% of the global population, are the fourth-largest religious group. Nearly 95% of Hindus reside in India. The Hindu population grew significantly in the Middle East-North Africa region by 62%, largely because of migration. In North America, it increased by 55%.
The Jewish population, the smallest group included in the study, grew modestly by 6%, rising from about 14 million to 15 million. Jews now account for 0.2% of the global population. The majority—45.9%—live in Israel, the highest proportion of any country. In the U.S., Jews make up about 2% of the population, a figure that includes religious Jews as well as secular individuals who identify culturally or ethnically as Jewish.
Migration patterns also influenced religious demographics in various regions. In the Gulf countries—Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the UAE—the influx of foreign-born residents led to increased numbers of non-Muslims, especially Hindus and Christians.
The Pew study is part of the Pew-Templeton Global Religious Futures project, which is funded by the Pew Charitable Trust and the John Templeton Foundation. This initiative explores shifts in global religious practices and their influence through extensive surveys and demographic analysis.