leurl7

So what? Statistics is not about fitting data points on a curve... And arguably HR is even less about that!

An other way to present things is that helmets have some effectiveness: source http://en.wikipedia.org/wiki/Bicycle_helmet#Meta-analyses

So at least use a one instead of none.

Even if it has some merits on some points, http://www.bicycling.com/senseless/index.html is too much misleading and not that really seriously researched, cf. http://www.bhsi.org/bicyclingmag1305.htm

A current certified helmet is already very useful, even a simple one.