The study, which is a snapshot of world religions in 2010 and does not show trends, brings to light a unique religious landscape that's defined by a burgeoning Islam, a shifting Christianity and a large group of religiously unaffiliated. It took Pew three years to compile.
Five big takeaways from the study:
1.) Muslims and Hindus are noticeably young
The median age of Muslims (23) and Hindus (26) is significantly lower than the global median age of 28 years old.
“Those with a large share of adherents in fast-growing, developing countries tend to have younger populations,” the Pew report says. “Those concentrated in China and in advanced industrial countries, where population growth is slower, tend to be older.”
Other than Muslims and Hindus, all other religious groups have a median age that is older than the global median.
“Christians have a median age of 30, followed by members of other religions (32), adherents of folk or traditional religions (33), the religiously unaffiliated (34) and Buddhists (34),” reads the study. “Jews have the highest median age (36), more than a dozen years older than the youngest group, Muslims.”
According to Hackett, these young median ages for Muslims and Hindus are largely because of high fertility rates and “indicates that they have a significant growth potential.”
2.) The world is faithful and diverse
According to numbers compiled by Pew, more than 80% of the world’s population identifies with a religious group.
While Christians are the largest group, with 31.5% of the global population, Muslims (23.2%), the unaffiliated (16.3%) and Hindus (15%) together make up more than half of the global population.
Jews, a religious group that makes up 2% of the United States, have a tiny share of the global pie. Only .2% of the global population practices Judaism, a number that puts the religion behind Buddhists (7.1%), folk religionists (5.9%) and a combination of religions like the Baha’i faith, Jainism, Sikhism, Shintoism, Taoism, Tenrikyo, Wicca and Zoroastrianism (1%).
3.) The unaffiliated are third largest global group, equal with Catholics
The religiously unaffiliated, a group that has experienced marked growth in the United States, make up 16% of people worldwide, according to the Pew survey. With 1.1 billion people worldwide, the number of religious unaffiliated people is equal to the number of Catholics.
The Asia-Pacific region dominates that number, where almost 900 million, or 76% of the worldwide population of ‘nones’ – a term used to describe people with no religious affiliation – reside.
China, with 700 million, boasts the largest population of religious nones. The Chinese government mandates state atheism, a practice that promotes the practices of disbelief and, in some cases, suppresses religious freedom.
The Pew study acknowledges that getting accurate numbers that reflect religious populations in China is extremely difficult, largely because the country does not conduct a census to understand the faithful. In their methodology, the study states that “the unaffiliated are all who do not identify with one of the other religions.”
“For China, we had to look at a number of different sources to come up with estimates for all the groups we looked at,” said Brian J. Grim, a senior researcher at Pew.
Previous studies of nonbelievers in China have found numbers much smaller than the one published by Pew. According to Grim, this stems from how you define belief.
“This study does not look particularly at whether people believe in god or believe in a higher power,” Grim said. “If you look at just belief, you would find a much larger number of Chinese people that believe in some supernatural force.”
Grim went on to say that if the definition of belief was broadened, the number of Chinese folk religions, which currently makes up 21.9% of the country, would increase and the number of nonbelievers in China would go down.
Japan, with 72 million, boasts the second largest population of religious nones, followed by the United States, with around 50 million religiously unaffiliated – or 16.4% of the countries population.
“The unaffiliated population in China is almost twice the entire population of the United States,” Hackett points out.
These nonbelievers are also younger than their religious brethren. In Africa, North America, South America and Europe, the unaffiliated median age is lower than the age of the faithful. The overall average age of the unaffiliated – 34 years old – is pulled up, however, by the mass of followers in Asia.
In previous studies – like a study released by Pew in October – this lower average age has some demographers assuming that this group will be growing in the next few decades.
4.) Less than 1% of global Christian population resides in the religion's birthplace
Though Christianity emerged in the Middle East and North Africa, it's practiced by less than 1% of the population there.
A combined three-fourths of Christians now reside in Europe (26%), Latin America and the Caribbean (24%) and sub-Saharan Africa (24%). North America is home to over 12% of the global Christian population.
In the Middle East and North Africa, which includes Egypt, Israel, the Palestinian territories and Jordan, Christians are experiencing little growth, according to Conrad Hackett, a demographers with Pew.
“In Egypt, for example, it seems that the Christian population just hasn’t kept pace with the Muslim population,” Hackett said. “The data we have says they have lower fertility than the Muslim population.”
But the Pew report shows that Christianity has become dominant in other parts of the world. One-in-three people worldwide identify as Christian, and 87% of them live in a country that is majority Christian.
Of the 232 countries studied, 68% have Christian majorities, according to Pew.
5.) To Pew, this is the definitive study of world religions
Branding it as the “largest project of its kind to date,” Hackett says that the Pew study used censuses, large-scale demographic surveys and country specific general population surveys.
“In order to present data that are comparable across countries, this study focuses on groups and individuals who identify themselves in censuses, large-scale surveys and other sources as being members of five widely recognized world religions – Buddhism, Christianity, Hinduism, Islam and Judaism,” the survey says.
In total, Pew worked through data through 232 countries and territories that the United Nations Population Division provides 2010 estimates in.
About 45% of all the people in the world were counted by government-sponsored censuses, the study says.