There are about 1.6 billion Muslims around the world, or 23 percent of the global population. “The overwhelming majority (87-90 percent) are Sunnis, about 10-13 percent are Shia Muslims,” the study said.
Among the 1.1 billion unaffiliated people around the world, over 700 million, or 62 percent of them, live in China alone, where they make up 52.2 percent of the Chinese population.
Japan comes next with the second largest unaffiliated population in the world with 72 million, or 57 percent of the national population. After that comes the United States, 51 million people — 16.4 percent of all Americans — said they have no link to an established faith.
Make sure to visit pewresearch.org. You can read all the specifics there.