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.

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