Of course, clarity comes at the cost of detail. The map bands together various Christian and Islamic schools of thought that don’t necessarily accept each other as ‘true believers’. It includes Judaism (only 15 million adherents, but the older sibling of the two largest religious groups) yet groups Sikhism (27 million) and various other more numerous faiths in with ‘others’. And it doesn’t make the distinction between atheism (“There is no god”) with agnosticism (“There may or may not be a god, we just don’t know”).