>Of course, this doesn't mean that if somebody puts on a helmet for whatever reason, (s)he becomes a >more experienced, responsible, safer rider instantly. Not at all.

In fact you want to argue that current helmet wearers are safer than non-helmet wearers, but if you put a helmet on non-helmet wearers, then they would ride even less safely.

A reasonable theory, but doesn't have any statistical support.

\> In the USA, an increase in helmet use from 18% to 50% of cyclists over a decade was accompanied by >a 10% increase in head injuries. There was no clear evidence of any increase in cycle use, which may >have declined.
First problem-are the head injuries occuring in the helmeted population, or is there an increase in head injuries in the non-helmeted population? If you could show that people wearing helmets were getting head injuries at a higher rate than non-wearers, then you'd have an argument.

There are also many other things other things which have changed over that decade along with helmet use. For example:
popularity of mountain biking -> more injuries
frequency of suv's on streets
movement of people to car-focused suburbs
etc. etc.
protection due to helmet use my very well be masked by these changes.

> I was sort of hoping that we would go into interesting topics like this one: >http://www.cyclehelmets.org/1081.html[/QUOTE]

I'm not a material scientist, so i can't discuss joule absorption rates, other than to note that helmets designed for big impacts are less good at dissipating small impacts.

However, the point he makes about the problem with helmets retained by chinstrap alone is a good one. Those helmets suck to wear, and wearing a helmet only to have it fly off when you crash sucks even more.
however, the whole industry has really stepped up on this one. Any but the cheapest helmets you can buy these days have much better retention systems & are much easier to wear comfortably and securely than those produced a decade or so ago.