In the beginning, they were a nomadic people, owners of caravans and traders. After Medina (the first war of Islam) Muslims had to move and became more nomadic.
Today this is not the case. Recent census figures place the Muslim population at 1.57 billion people and growing.
Data from 232 countries and territories were gathered and analysed for the study, which the Pew Forum called "the largest project of its kind to date."