I'd guess that at least 50% of my peers left the religion in one way or another. Faded (before that was a term), DFd, etc. and I think the rate is even higher among JWs from my children's generation (children of our peers).
I am constantly surprised how many times one of my kids mentions that "he" or "so-and-so" is out when learning about former JW acquaintances from our Hall or Circuit. I'm thinking most families have at least some of their children who have left.