You mean if I drive a cage I might live forever?
Spew.
The one factor which was not measured, which will never be measured is the number of both groups which did not get in accidents, fatal or otherwise.
If you can see/hear what's coming you can avoid it.
That’s right. Helmets do greatly restrict side vision, as well your hearing, both of which are vital to your safety. Also, they can bounce off the pavement like a ping pong ball breaking the wearers neck while saving them from a severe head injury. Of course this statistic is one no one ever wants to mention. Just like seat belts, they can save you... or, they can hold you in position to be crushed to death. You never know.