From HERE:
Conversion growth is where you find quite a contrast. According to figures presented in the 2000 edition of the World Christian Encyclopedia, each year some 950,000 people convert to Islam from some other persuasion. Christianity, by contrast, sees some 2.7 million each year shift their affiliation to Christianity and presumably their allegiance to Christ from some other religion.
(Woodberry and Shubin 2001)
