Babies born to Muslims will begin to outnumber Christian births by 2035

More babies were born to Christian mothers than to members of any other religion in recent years, reflecting Christianity’s continued status as the world’s largest religious group. But this is unlikely to be the case for much longer: Less than 20 years from now, the number of babies born to Muslims is expected to modestly exceed births to Christians, according to new Pew Research Centre demographic estimates.

Muslims are projected to be the world’s fastest-growing major religious group in the decades ahead, as Pew Research Centre has explained, and signs of this rapid growth already are visible. In the period between 2010 and 2015, births to Muslims made up an estimated 31% of all babies born around the world – far exceeding the Muslim share of people of all ages in 2015 (24%).
The world’s Christian population also has continued to grow, but more modestly. In recent years, 33% of the world’s babies were born to Christians, which is slightly greater than the Christian share of the world’s population in 2015 (31%).

While the relatively young Christian population of a region like sub-Saharan Africa is projected to grow in the decades ahead, the same cannot be said for Christian populations everywhere. Indeed, in recent years, Christians have had a disproportionately large share of the world’s deaths (37%) – in large part because of the relatively advanced age of Christian populations in some places. This is especially true in Europe, where the number of deaths already is estimated to exceed the number of births among Christians. In Germany alone, for example, there were an estimated 1.4 million more Christian deaths than births between 2010 and 2015, a pattern that is expected to continue across much of Europe in the decades ahead.

Globally, the relatively young population and high fertility rates of Muslims lead to a projection that between 2030 and 2035, there will be slightly more babies born to Muslims (225 million) than to Christians (224 million), even though the total Christian population will still be larger. By the 2055 to 2060 period, the birth gap between the two groups is expected to approach 6 million (232 million births among Muslims vs. 226 million births among Christians).

In contrast with this baby boom among Muslims, people who do not identify with any religion are experiencing a much different trend. While religiously unaffiliated people currently make up 16% of the global population, only an estimated 10% of the world’s newborns between 2010 and 2015 were born to religiously unaffiliated mothers. This dearth of newborns among the unaffiliated helps explain why religious “nones” (including people who identity as atheist or agnostic, as well as those who have no particular religion) are projected to decline as a share of the world’s population in the coming decades.

By 2055 to 2060, just 9% of all babies will be born to religiously unaffiliated women, while more than seven-in-ten will be born to either Muslims (36%) or Christians (35%).
The projections do not assume that all babies will remain in the religion of their mother. The projections attempt to take religious switching (in all directions) into account, but conversion patterns are complex and varied. In some countries, including the United States, it is fairly common for adults to leave their childhood religion and switch to another faith (or no faith). For example, many people raised in the U.S. as Christians become unaffiliated in adulthood, and vice versa – many people raised without any religion join a religious group later in their lives. But in some other countries, changes in religious identity are rare or even illegal.

Global population projections, 2015 to 2060
Christians were the largest religious group in the world in 2015, making up nearly a third (31%) of Earth’s 7.3 billion people. Muslims were second, with 1.8 billion people, or 24% of the global population, followed by religious “nones” (16%), Hindus (15%) and Buddhists (7%). Adherents of folk religions, Jews and members of other religions make up smaller shares of the world’s people.
Between 2015 and 2060, the world’s population is expected to increase by 32%, to 9.6 billion. Over that same period, the number of Muslims – the major religious group with the youngest population and the highest fertility – is projected to increase by 70%. The number of Christians is projected to rise by 34%, slightly faster than the global population overall yet far more slowly than Muslims.

As a result, according to Pew Research Centre projections, by 2060, the count of Muslims (3.0 billion, or 31% of the population) will near the Christian count (3.1 billion, or 32%).
Except for Muslims and Christians, all major world religions are projected to make up a smaller percentage of the global population in 2060 than they did in 2015. While Hindus, Jews and adherents of folk religions are expected to grow in absolute numbers in the coming decades, none of these groups will keep pace with global population growth.

Worldwide, the number of Hindus is projected to rise by 27%, from 1.1 billion to 1.4 billion, lagging slightly behind the pace of overall population growth. Jews, the smallest religious group for which separate projections were made, are expected to grow by 15%, from 14.3 million in 2015 to 16.4 million worldwide in 2060.5 And adherents of various folk religions – including African traditional religions, Chinese folk religions, Native American religions and Australian aboriginal religions, among others – are projected to increase by 5%, from 418 million to 441 million.

Buddhists, meanwhile, are projected to decline in absolute number, dropping 7% from nearly 500 million in 2015 to 462 million in 2060. Low fertility rates and aging populations in countries such as China, Thailand and Japan are the main demographic reasons for the expected shrinkage in the Buddhist population in the years ahead.

All other religions combined – an umbrella category that includes Baha’is, Jains, Sikhs, Taoists and many smaller faiths – also are projected to decrease slightly in number, from a total of approximately 59.7 million in 2015 to 59.4 million in 2060.

The religiously unaffiliated population is projected to shrink as a percentage of the global population, even though it will increase modestly in absolute number. In 2015, there were slightly fewer than 1.2 billion atheists, agnostics and people who did not identify with any particular religion around the world. By 2060, the unaffiliated population is expected to reach 1.2 billion. But as a share of all people in the world, religious “nones” are projected to decline from 16% of the total population in 2015 to 13% in 2060. While the unaffiliated are expected to continue to increase as a share the population in much of Europe and North America, people with no religion will decline as a share of the population in Asia, where 75% of the world’s religious “nones” live.

Geographic differences like these play a major role in patterns of religious growth. Indeed, one of the main determinants of future growth is where each group is geographically concentrated today. For example, the religiously unaffiliated population is heavily concentrated in places with aging populations and low fertility, such as China, Japan, Europe and North America. By contrast, religions with many adherents in developing countries – where birth rates are high and infant mortality rates generally have been falling – are likely to grow quickly. Much of the worldwide growth of Islam and Christianity, for example, is expected to take place in sub-Saharan Africa.

Change in where groups are concentrated
The regional distribution of religious groups is also expected to shift in the coming decades. For example, the share of Christians worldwide who live in sub-Saharan Africa is expected to increase dramatically between 2015 and 2060, from 26% to 42%, due to high fertility in the region. Meanwhile, religious switching and lower fertility will drive down the shares of the global Christian population living in Europe and North America.

Sub-Saharan Africa is also expected to be home to a growing share of the world’s Muslims. By 2060, 27% of the global Muslim population is projected to be living in the region, up from 16% in 2015. By contrast, the share of Muslims living in the Asia-Pacific region is expected to decline over the period from 61% to 50%. The share of Muslims in the Middle East and North Africa is expected to hold steady at 20%.

Age and fertility are major factors behind growth of religious groups.
The current age distribution of each religious group is an important determinant of demographic growth. Some groups’ adherents are predominantly young, with their prime childbearing years still ahead, while members of other groups are older and largely past their childbearing years. The median ages of Muslims (24 years) and Hindus (27) are younger than the median age of the world’s overall population (30), while the median age of Christians (30) matches the global median. All the other groups are older than the global median, which is part of the reason why they are expected to fall behind the pace of global population growth.

Moreover, Muslims have the highest fertility rate of any religious group – an average of 2.9 children per woman, well above replacement level (2.1), the minimum typically needed to maintain a stable population. Christians are second, at 2.6 children per woman. Hindu and Jewish fertility (2.3 each) are both just below the global average of 2.4 children per woman. All other groups have fertility levels too low to sustain their populations.

Between 2015 and 2020, Christians are projected to experience the largest losses due to switching. Globally, about 5 million people are expected to become Christians in this five-year period, while 13 million are expected to leave Christianity, with most of these departures joining the ranks of the religiously unaffiliated.
The unaffiliated are projected to add 12 million and lose 4.6 million via switching, for a net gain of 7.6 million between 2015 and 2020. The projected net changes due to switching for other religious groups are smaller.

How births and deaths are changing religious populations
As the world’s largest religious group, Christians had the most births and deaths of any group between 2010 and 2015. During this five-year period, an estimated 223 million babies were born to Christian mothers and roughly 107 million Christians died, meaning that the natural increase in the Christian population – i.e., the number of births minus the number of deaths – was 116 million over this period.

Muslims had the second-largest number of births between 2010 and 2015, with 213 million babies born to Muslim mothers. But Muslims saw the largest natural increase of any religious group – more than 152 million people – due to the relatively small number of Muslim deaths (61 million). This large natural increase results from both high Muslim fertility and the concentration of the Muslim population in younger age groups, which have lower mortality rates.

Compared with the overall size of the religiously unaffiliated population (16% of the world’s people), there were relatively few recent births to unaffiliated mothers (10% of all births between 2010 and 2015). Religious “nones” are the third-largest group overall, and yet due to lower levels of fertility, they rank fourth behind Hindus in terms of babies born. Between 2010 and 2015, an estimated 68 million babies were born to unaffiliated mothers, compared with 109 million to Hindu mothers. Hindus also saw a much larger natural increase than the religiously unaffiliated (67 million vs. 26 million).