Thank you!
Funnily enough, we were always reminded in school how Islam was the fastest growing religion (with most converts being women), but never learned about the people who left. If you never get told about them, you start to think they don't exist.

Yeah mine was from my parents
I'm betting that the women (or maybe most of the women) who convert are the wives of Muslim men. Either they feel pressured to do so or fall for the prettier parts of the faith. I doubt they came to it on their own.
Also, I've learned not to take the "Fastest Growing Religion" slogan seriously. Every faith claims it once and a while. The Mormon Church and Scientology are both claiming it now in America.
Well if you consider muslims are a lower number in the states. If they do increase a bit. They would have a higher percentage then anyone else. For example if a group of religious believers have 100 followers, and they get 50 followers in whatever way you could imagine. Then they have a 50% increase. Where if a group of 10,000 gets 50. They get only a .5% increase. So any where the groups are smaller, then the easier it is to claim they are the fastest growing religion.
I also agree the increase is either in muslim men converting the wives, or from the offspring (being that most the arabs I know have more then 5 kids).