H*lmets again - new study - sorry

[Zog The Undenia]

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

 

[Tony Raven]

Zog The Undeniable wrote:
> 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

 

[Just Zis Guy]

On Wed, 16 Jun 2004 18:52:04 +0100, Zog The Undeniable
<[email protected]> wrote in message <40d08a14.0@entanet>:

>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

 

[Mark]

"Tony Raven" wrote ...
> Zog The Undeniable wrote:
> > 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
>
>
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

 

[Brendan Halpin]

Zog The Undeniable <[email protected]> writes:

> 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
mailto:[email protected]
http://www.ul.ie/sociology/brendan.halpin.html

 

[Just Zis Guy]

mark wrote:

> 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

 

[Simon Brooke]

in message <[email protected]>, Just zis Guy, you know?
('[email protected]') wrote:

> 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 protected] (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

 

[Just Zis Guy]

Simon Brooke wrote:

>> Maybe they are using Cook & Sheikh helmets?
> I thought it was Sheikh and Bake?

Or is it Sheikh and Vac[uous]?

> 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

 

[David Martin]

On 17/6/04 10:35 pm, in article
[email protected], "Simon Brooke"
<[email protected]> wrote:

> 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