H*lmets again - new study - sorry

Zog The Undeniable said:

Guy, can you provide an eloquent rebuttal for this one? It was posted
to r.b.t and I note the researchers have dragged up the discredited 85%
figure again.

http://economics.uta.edu/grant/helmet.pdf

Having read through briefly they appear to make a fairly standard mistake.
They count head injuries in juveniles compared to adults and pedestrians
across the introduction of a state helmet law. They find head injuries
decline in the juvenile population and ascribe this to the helmet law. In a
sense they are correct - the helmet law has caused a reduction in head
injuries in juveniles. However they have not examined the causal link. The
usual reason the head injuries decline is because it puts juveniles off
cycling so less cyclists, less head injuries. The only discussion they make
of this is to factor out long term trends in cycling levels (while ignoring
the step change the laws create) and to comment there was no evidence of cycle
journeys being substituted by car or pedestrian journeys. When the fewer
cyclists has been factored in, most studies find that the decline in cyclist
numbers was greater than the decline in head injuries i.e the risk of head
injury for those that still cycled went up. The authors make the mistake here
of ignoring this crucial effect instead trying mistakenly to ascribe the
change in head injuries to the protective effect of the helmet. The most
effective way though to stop all cyclist head injuries is to stop people
cycling and these helmets laws go some way along the way to achieveing that.

Tony

Zog The Undeniable said:

http://economics.uta.edu/grant/helmet.pdf

Looks like another meta-analysis based on the same fallacies (e.g. not
adjusting for exposure, as Tony says). I'll look into it in more
detail. The authors have no particular history and of the
acknowledgees I don't know of any save The Safe Kids Campaign, which
is funded by Bell.

It sounds implausible, since in the USA as a whole helmet use has
risen from 18% to 50%, and in the same period the injury rate has
risen by 40%.

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at Washington University

"Tony Raven" wrote ...

Quoted message said:

Zog The Undeniable said:

Guy, can you provide an eloquent rebuttal for this one? It was posted
to r.b.t and I note the researchers have dragged up the discredited 85%
figure again.

http://economics.uta.edu/grant/helmet.pdf

Having read through briefly they appear to make a fairly standard mistake.
They count head injuries in juveniles compared to adults and pedestrians
across the introduction of a state helmet law. They find head injuries
decline in the juvenile population and ascribe this to the helmet law. In

a

Quoted message said:

sense they are correct - the helmet law has caused a reduction in head
injuries in juveniles. However they have not examined the causal link.

The

Quoted message said:

usual reason the head injuries decline is because it puts juveniles off
cycling so less cyclists, less head injuries. The only discussion they

make

Quoted message said:

of this is to factor out long term trends in cycling levels (while

ignoring

Quoted message said:

the step change the laws create) and to comment there was no evidence of

cycle

Quoted message said:

journeys being substituted by car or pedestrian journeys. When the fewer
cyclists has been factored in, most studies find that the decline in

cyclist

Quoted message said:

numbers was greater than the decline in head injuries i.e the risk of

head

Quoted message said:

injury for those that still cycled went up. The authors make the mistake

here

Quoted message said:

of ignoring this crucial effect instead trying mistakenly to ascribe the
change in head injuries to the protective effect of the helmet. The most
effective way though to stop all cyclist head injuries is to stop people
cycling and these helmets laws go some way along the way to achieveing

that.

Quoted message said:

Tony

One of the footnotes in the study mentions a 12% reduction in fatalities and
a 20% reduction in bicycle usage in the 1990's. The authors sem to have
conveniently ignored their own footnote in making their claims.
--
mark

mark said:

One of the footnotes in the study mentions a 12% reduction in
fatalities and a 20% reduction in bicycle usage in the 1990's. The
authors sem to have conveniently ignored their own footnote in making
their claims.

They also seem to have ignored the pre-existing trends and the very similar
trend among child pedestrians. Maybe they are using Cook & Sheikh helmets?

--
Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

Zog The Undeniable said:

Guy, can you provide an eloquent rebuttal for this one? It was
posted to r.b.t and I note the researchers have dragged up the
discredited 85% figure again.

http://economics.uta.edu/grant/helmet.pdf

It's a quite sophisticated paper from a statistical point of view,
strongly based in economics. You can also see that the authors have
thought pretty hard about the issue (sensible comments about risk
compensation, etc.). The big weakness of the cost-benefit analysis
is that they completely ignore the value of forgone cycling (and
its mid- and long-term health consequences). Their only basis for
doing this is that there is no significant effect of child-helmet
laws on miles driven. As remarked, footnote 6 shows they are aware
of the declining trend. It's a remarkably weak test for a
cycling-reduction effect, if one considers the number of
person-miles cycled by children, and the small proportion of that
which is "necessary" transport rather than play, in comparison with
the huge number of miles driven (it's all they have in the dataset,
but it is far too weak to depend on).

It's a good economics paper, which means its conclusions are as
good as its assumptions. Ignoring the level of child-cycling clouds
the conclusion, but it is still correct: helmet laws reduce
fatalities partly (perhaps primarily) by reducing cycling. If I
were refereeing this for a journal, I would simply ask for this to
be acknowledged centrally in the discussion (and for them to drop
the 85% claim -- how can they not contest this when they come up
with 15% in their own research???).

Brendan
--
Brendan Halpin, Department of Sociology, University of Limerick, Ireland
Tel: w +353-61-213147 f +353-61-202569 h +353-61-390476; Room F2-025 x 3147
[email hidden] http://www.ul.ie/sociology/brendan.halpin.html

in message <[email hidden]>, Just zis Guy, you know?

(') said:

trend among child pedestrians. Maybe they are using Cook & Sheikh
helmets?

I thought it was Sheikh and Bake?

Incidentally seeing it's Edinburgh and child health, is the Cook Robin's
ex-wife?

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
Just as defying the law of gravity through building aircraft requires
careful design and a lot of effort, so too does defying laws of
economics. It seems to be a deeply ingrained aspect of humanity to
forever strive to improve things, so unquestioning acceptance of a
free market system seems to me to be unnatural. ;; Charles Bryant

Simon Brooke said:

Quoted message said:

Maybe they are using Cook & Sheikh helmets?

I thought it was Sheikh and Bake?

Or is it Sheikh and Vac[uous]?

Quoted message said:

Incidentally seeing it's Edinburgh and child health, is the Cook
Robin's ex-wife?

No idea - I guess not or someone would surely have mentioned it before.

--
Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

On 17/6/04 10:35 pm, in article
[email hidden], "Simon Brooke"

Quoted message said:

Incidentally seeing it's Edinburgh and child health, is the Cook Robin's
ex-wife?

Seeing as his name is adrian and he works in London, probably not.

...d