I think it's the huge media exposure on concussion with superstars such as Crosby getting more injured and more and more research and advancements in the field of head injuries that give the impression that concussions are "on the rise" which I doubt they are. (10 years ago, medical research on concussion wasn't nearly as advanced as it is today, nor have concussion symptoms been looked upon as serious (See: Lindros)). However, with players becoming faster, and bigger than they were years ago, and with advances in equipment such as skates and padding, players are hitting harder than ever which could lead to the rise.