Those who have no religion now make up the third largest religious group in the world, according to a new study by Pew Forum on Religion and Public Life.
The study, called "The Global Religious Landscape," found that Christians including Catholics are still number one, making up about 32 percent of the world's population. They are followed by Muslims with twenty-three percent.
But about 16 percent of the world's population has no religion, the study showed. The "unaffiliated" consist of those who profess no religion: atheists, agnostics, and people with spiritual beliefs but no link to any established faith.
"Many of the religiously unaffiliated do hold religious or spiritual beliefs," the study stressed.
"Belief in God or a higher power is shared by 7 percent of unaffiliated Chinese adults, 30 percent of unaffiliated French adults, and 68 percent of unaffiliated U.S. adults," the report said.
Christianity is evenly spread across all regions of the world, a stark contrast to Hinduism which is the least global. Ninety-four percent of its population is found in India.
The study estimated Christianity was the largest faith with 2.2 billion adherents, or 31.5 percent of the world's population.
But it showed alarming projected expansive growth for Islam and Hinduism in the future while Jews have the weakest growth prospects.
The findings were based on 2010 data and issued by the Pew Forum on Religion and Public Life on Tuesday.