Where are the greatest concentration of the four major religions today?

The four greatest religions nowadays are:

- Christianity; mostly concentrated in Europe, North America, South America.

- Islam; mostly concentrated in North Africa, the Middle East, western part of South Asia, and the southern half of Southeast Asia.

- Buddhism; mostly concentrated in East Asia, and the northern half of Southeast Asia.

- Hinduism; almost all followers of this religions are concentrated in South Asia.