Faulty studies as pointed out Phil. There is no proof that the lack of a helmet caused the deaths. Even if they said person x died form head trauma and they weren't wearing helmet, doesn't mean they couldn't have also died from head trauma if they were wearing a helmet. Plus they have no way of knowing how many riders actually rode during that time period. It could have been hundreds or thousands more riders on the road in that year.
You gotta apply a little logic when it comes to helmets.. What is it and how does it protect you? That kinda thing.
If you came off your bike at 75mph and were lucky enough to slide with no major impacts, then a helmet WOULD protect you from sliding damage, it would also protect your head against punctures from sliding over stones 1" or less, the helmet would be punctured, not your head..
If you hit something at 75mph. Completely different ballgame.. You are gonna be pushing up roses. The body can't withstand that kind of trauma, your brain would swell, organs would burst, your neck would break, that kinda thing..
Even at 35mph, you hit something head on.. Other than Possibly - Possibly - avoiding a major skull compression - A helmet isn't going to save you.. Because your brain is going to swell and spinal injuries are almost guaranteed (in head on situations).
Glancing blows.. A helmet might help more regarding fractures and help prevent loss of bits of your face, but that brain is still gonna be ping-ponging around inside your skull which is going to do damage to some degree..
Falling off your bike and smacking your head on the concrete? MMmm.. You'll likely have a headache, but almost certainly, no fractures...
Helmets aren't magic.. They offer a realistic amount of protection and are effective at preventing certain injuries in some situations.. But I think a lot of people see them as security against death on a bike..
I think that's how helmets are sold by statistics.
.. Unfortunately not..
I see them as protection against sliding damage, against small puncture injuries. I see them as a help to prevent fractures in low impact situations, a good helmet will keep your head streamlined which reduces fatigue at higher speeds, keeps the bugs and road bees from beating you up too bad over the long haul... Not much more than that.
But.. Realistically.. If you come off your bike.. I would be relying more on luck than a helmet to save you.