I wonder if their stats are right. I thought the number of non-believers was supposed to increase rather than decrease
I think people are leaving religious institutions but seem to still believe in things unseen, because that's just human nature. A high percentage of folks on this site say they are "spiritual but not religious", and many believe in a sort of universal "energy" or "connectedness" or reincarnation, or telepathy, etc. Humans are always human, even when we occasionally change our packaging.
I think that the level of non believers increases with one's mental acumen. Scientists, Mathematicians, Artists, Writers, and Philosophers are among those who are able to step into this arena with serious thoughts and deliberations. Your typical fundamentalist is a mindless cadaver who sits in awe to who ever is on stage spewing his mindless rants on salvation and what the truth is while spewing bigotry, racism on all those who haven't a clue.