Hi T4p, can I just say that it is impossible to say. Big problem is that many of them are persecuted all over the place, therefore they go underground.
The press says that Islam is the fastest growing religion.
The problem for Christianity has always been that the more popular the faith the shallower the commitment. In America it might cover the land but it is only inch thick. When Constantine converted the Roman empire it stopped the persecution but it also started the dark ages.
I would therefore be wary on relying too much on numbers per se.
