The largest and the second-largest religious group by country
According to Pew Research:
Religiously unaffiliated people – sometimes called the “nones” – account for 16% of the world’s population, and they make up the largest “religious group” in seven countries and territories. Perhaps more remarkably, they also are the second-largest group in roughly half (48%) of the world’s nations.
Indeed, while either Christians or Muslims make up the largest religious group in nine-in-ten nations around the globe, “nones” rank second in size in most of the Americas and Europe, as well as in many countries in sub-Saharan Africa.