Head Injuries. Am I right, or have I suffered a few too many

While reading through The Effectiveness of Bicycle Helmets:A Review[1] in
section 2.3 paragraph 3, it quotes a study by Piggott et al, 1994[2] as
saying that

"The prevalence of head injuries among hospital admissions was 32 per
cent .... although for only 5 per cent was the head injury categorised as
being more than minor"

Sorry, what was that again?

"for only 5 per cent was the head injury categorised as being more than
minor"

So unless my brain is failing me again[3], and if this study is right and
the results are comparable across all hospitals:

1. 95% of the head injuries in hospital admissions in this study are
minor.
2. With plenty of exceptions, it is a broad rule that the harder the
impact, the more the damage.
3. Helmets protect better against impacts of a smaller force than of a
larger force.
4. So if x% of head injuries are prevented by wearing a helmet, then that
will generally be the least serious x%
5. So to start preventing significant amounts of serious head injuries
cycle helmets would have to reduce head injuries by more than 95% - and
that's just the ones serious enough to make people pop into the hospital!

I have two questions.

A) Is there a flaw in my logic?
B) Is the 5% figure valid for UK hospitals?



[1]
Revised Edition Prepared by Dr. Michael Henderson
for the Motor Accidents Authority of New South Wales, Australia.
1995
http://www.helmets.org/henderso.htm

[2]
Piggott P, Knuiman M W and Rosman D L, Rates and pattern of injuries from
bicycle crashes based on population: police and hospital data, Rood and
Transport Research, 3:64-74, 1994.

[3]
Postage and packaging free...