: The question of whether numerical growth is from population growth or conversion is HOTLY debated. There is no way to confirm any claims of having the most converts. If you want to put a billion instead of millions, that's fine, but the bit about "fastest growing" smacks of triumphalism, advertising, boasting, whatever. It's unpleasant. It reminds me of the Mormons and the Bahai I met when I was doing the fieldwork for my PhD, both of whom boasted about being the fastest growing religion. Based on, so far as I could tell, suspect statistics.  Frex, the Bahais said that the small village where I lived had twenty Bahais, or something like that, and what they did have was a young bachelor of questionable character who had attended one meeting.  

 : I think this topic has been discussed at length in Islam in the United States. If you feel that Islamic population growth deserves extended treatment, perhaps we should set up a page for it and adjourn the discussion there. It's too large a topic to handle in one sentence in a page on an entirely different subject.