Religious compositions vary a lot from country to country.

In my own country, the United Kingdom, Christianity is the most popular, and following no religion is becoming increasingly common, particularly among young people. But I struggle to get a sense of how these differences stack up globally.

The Pew Research Center publishes estimates of religious affiliation across the world. You can see the global breakdown in the chart for 2020 (the most recent year available). It shows the number of people who identify with each religion. Pew counts people by the religion they report, regardless of their beliefs or practices.

You can see that Christians are the largest group, with 2.3 billion people, followed by Muslims, with 2 billion. People with no religious affiliation come close behind.

Those not affiliated with any religion are among the largest groups in the world. But this undersells religion’s reach: when we add up all religious groups, most people in the world — around three in four — identify with a religion. Those with no religious affiliation are still a minority.