A Pew Research Center study found that Muslims are the fastest growing religious group worldwide. Between 2010 and 2020, the global Muslim population grew by 347 million, more than all other religions combined, mainly due to higher birth rates.
Christianity also grew, adding 122 million followers, but its share of the global population slightly declined. Despite this, Christianity remains the largest religion, with 2.3 billion people, making up nearly 29% of the world’s population.
The study used 2,700 sources like national censuses and surveys, covering 100,000 people in 201 countries. Most respondents were simply asked which religion they identified with.