By LAURIE GOODSTEIN
Published: December 18, 2012
A global study of religious adherence released on Tuesday by the Pew Research Center found that about one of every six people worldwide has no religious affiliation. This makes the “unaffiliated,” as the study calls them, the third-largest group worldwide, with 16 percent of the global population — about equal to Catholics.
The study also found a wide disparity in the median age of religious populations, with Muslims and Hindus the youngest, and Buddhists and Jews the oldest. The median age of the youngest group, Muslims, was 23, while the median for Jews was 36.
Over all, Christians (including Catholics) are the largest religious group, with 2.2 billion people, about 32 percent of the world’s population. They are followed by Muslims, with 1.6 billion, about 23 percent. There are about one billion Hindus, about 15 percent of the global population, and nearly half a billion Buddhists, about 7 percent.
The study, “The Global Religious Landscape,” is a snapshot of the size and distribution of religious groups as of 2010, and does not show trends over time.
“Something that may surprise a lot of people,” said Conrad Hackett, a primary researcher on the report, “is that the third-largest religious group, after Christians and Muslims, is the religiously unaffiliated. There may have been some guesses floating out there before, but this is the first time there are numbers based on survey data analyzed in a rigorous and scientific way.”
More than three-quarters of the religiously unaffiliated live in Asia, the majority in China. Many of the people in this group do hold some religious or spiritual beliefs and may even believe in a deity, but they do not identify with a particular faith.
People who practice folk or tribal religions, like African, Chinese, American Indian and Australian aboriginal traditional religions, make up another 6 percent of the world’s population. Smaller faith groups — like Bahais, Jains, Sikhs, Shintoists, Taoists, Wiccans and Zoroastrians — combined make up less than one percent of the global population. Jews, with about 14 million, make up only 0.2 percent of the global population.
The study is based on analysis of 2,500 different data sources, including censuses and demographic surveys of children and adults in 232 countries. It relies on self-identification, so it includes people who are not regular practitioners or orthodox believers of the religion they claim.
The religious groups with the youngest median ages have the highest levels of fertility and poverty and the lowest levels of female education, Jack A. Goldstone, director of the Center for Global Policy at George Mason University, in Virginia, said in an interview by e-mail. He noted that in predominantly Muslim countries where the government supports the education of women and girls, like Tunisia, Iran and Indonesia, the median age is higher than for Muslims in Africa and the Middle East.
The study also shows that about one-fourth of the world’s population lives in countries where they are a religious minority. But 97 percent of Hindus and 87 percent of Christians live in countries where they are the majority faith, said Alan Cooperman, associate director for research at the Pew Forum.
“Christians are the most evenly dispersed — except in one place, and that’s the Middle East and North Africa, which happens to be the place where Christianity originated,” Mr. Cooperman said.