Islam Fact Box

Report: Top 10 Muslim countries, by population

1. Indonesia: 202,867,000 (country is 88.2 percent Muslim)

2. Pakistan: 174,082,000 (country is 96.3 percent Muslim)

3. India: 160,945,000 (country is 13.4 percent Muslim)

4. Bangladesh: 145,312,000 (country is 89.6 percent Muslim)

5. Egypt: 78,513,000 (country is 94.6 percent Muslim)

6. Nigeria: 78,056,000 (country is 50.4 percent Muslim)

7. Iran: 73,777,000 (country is 99.4 percent Muslim)

8. Turkey: 73,619,000 (country is about 98 percent Muslim)

9. Algeria: 34,199,000 (country is 98 percent Muslim)

10. Morocco: 31,993,000 (country is about 99 percent Muslim)

Roughly nine out of 10 Muslims worldwide are Sunni, and about one in 10 is Shiite, they estimated.They warned they were less confident of those numbers than of the general population figures because sectarian data is harder to come by.Only one or two censuses in the world ... have ever asked the sectarian question.Among Muslims it's a very sensitive question. If asked, large numbers will say I am just a Muslim -- not that they don't know, but it is a sensitive question in many places.

One in three of the world's Shiite Muslims lives in Iran, which is one of only four countries with a Shiite majority, he said. The others are Iraq, Azerbaijan, and Bahrain.

Source: "Mapping the Global Muslim Population," The Pew Forum on Religion & Public Life.