That's interesting, not too long ago I had a lively discussion with a buddy that rides a HD. Of course he wears one of those beanie helmets. He was trying to tell me that the heavy full face helmets will break your neck in a crash. Well I think you would have to be one hell of a pencil neck for that to happen. I couldn't convince him.I am a retired firefighter, and I have seen what happens to people who wear those beanie helmets, NOT pretty.
I've heard that argument, too, and it's the same logic that brought us "loud pipes save lives." No logic or data, in other words, just uninformed speculation, wishful thinking, and this-is-how-I-want-it-to-be magic.
Now, I can see a high-speed impact with a sudden deceleration of a restrained driver (i.e. race car into a wall) having neck problems, but a biker won't stay with his bike such situations, and thus there is no neck stress.
I guess the weight of the helmet added to the weight of the concrete-filled skull. . . . .
Back on-topic, I thought I'd check, and the percentages
do add up to 100!