New demographic data highlights just how concentrated religious identity is in some parts of the world. According to figures compiled by World Population Review and the Pew Research Centre, a small number of countries have populations that are overwhelmingly Christian or Muslim, often exceeding 97–99% adherence to a single faith.

In the early centuries of recorded history, Hinduism emerged as the dominant global religion. Rooted in the Indian subcontinent, it held the largest following for much of ancient and medieval history due to population growth and cultural consolidation in South Asia.