From: lambert@spectrum.cs.unsw.oz.au (Tim Lambert)
Subject: Re: NSW homicides
Organization: none
	<1992Oct3.003654.18954@CSD-NewsHost.Stanford.EDU>
	<LAMBERT.92Oct6170352@henna.spectrum.cs.unsw.oz.au>
	<1992Oct8.003530.18632@CSD-NewsHost.Stanford.EDU>
Date: Tue, 13 Oct 1992 17:45:07 GMT

>>>>> On Thu, 8 Oct 1992 00:35:30 GMT, andy@SAIL.Stanford.EDU (Andy Freeman) said:

> (Tim Lambert) writes:
>>(Andy Freeman) said:

>>What on earth do you mean by 'the "nothing else happened"
>>parameter"?

> Lambert's model is for a transition between two stable situations with
> some "noise".  He uses it to argue that gun control explains the
> transition.  Yet, he doesn't bother to show whether or not anything
> else happened at the relevant time, whether or not the situations were
> in fact stable, and so on.

You call this a "parameter"??  This is a bizarre usage even by your
standards.  Your claim that I have not shown that the situations were
stable is false.  The homicide rate was roughly constant in the period
before gun control and in the period after gun control.  Whatever
effects other factors may have had on the homicide rate in these
periods are lost in the noise.

I do not claim that the data proves that gun control caused the
change, but it is more plausible than any other explanation offered so
far:

1. In the book from which I extracted the original data, Wallace
suggests that the change was caused by a decline in infanticide.
Indeed, there was a decline in infanticide, but not sufficient to
explain the observed change -- i.e. if we exclude infanticides from
the data the drop is still statistically significant.

2. It might be that demographic change caused the decline i.e. a
decrease in the percentage of young men in the population.  However,
the demographic change associated with WWI when 40% of the males 18-45
enlisted, is far far larger than any other change during the period,
and the homicide rate 1915-18, while lower than the surrounding years
is still higher than the post gun control rate.  Furthermore,
correcting for the demographic effects of WWI destroys the "gradual
decline" model -- it does not fit the adjusted homicide rates at all
well.

3. Perhaps changes in unemployment and poverty caused the decrease.
This seems unlikely since the Depression does not seem to have
affected the homicide rate at all.

4. Maybe the decrease was caused by increasing urbanization.  This
seems unlikely since urbanization increased gradually over the period
1900-1970, not abruptly around 1920.

5. If some other factor is supposed to explain the decrease, it must
explain why the rate did not decrease in the adjacent states of
Queensland and South Australia until they introduced gun control (in
1927 and 1929 respectively).  It must also explain why the rate for
homicide by "other means" did not decrease significantly after 1920,
but the firearm homicide rate did.

>>Model                        Parameters   Andy-parameters
>>1. Abrupt change in 1920              2               2+n
>>2. Decline starting in 1910           4               4+n
>>
>>either way, the abrupt change model is simpler.

> So?  As n increases, the difference becomes less and less important.
> In any event, we're not looking for the simplest model, we're looking
> for good models.  More importantly, not all parameters are equally
> important, so the addition is rather inappropriate.

 On January 15 1605, Johannes Kepler might have said:
]] My model of an ellipse (two parameters -- lengths of major and
]] minor axes) for the orbit of Mars is to be preferred to
]] Copernicus's 5 epicycles because it is so much simpler.

 and a 17th century Andy Freeman might have replied:
] Kepler misrepresents the simplicity of his model.  There are many
] more parameters than two.  Where to put the centre of the ellipse,
] which observations to use when fitting the ellipse, the "nothing
] else happened" parameter etc etc.  As we consider all these
] parameters, the difference between the elliptical model and the
] epicyclic model becomes less and less important. In any event,
] we're not looking for the simplest model, we're looking for good
] models. A 27 epicycle model fits the data better than the ellipse,
] so if there are problems with the 5 epicycle model we should move to
] the 27 epicycle model.

>>Strawman.  Just because you can construct an implausible explanation where
>>gun-control caused the decline, it does not follow that all such
>>explanations are implausible.

> It wasn't an implausible explanation, it was a number of factors that
> the "gun control worked in a step fashion" advocates must address.
> People don't work the way that model assumes.

Pull the other one Andy.  You claim that it could not cause an abrupt
change because that would require the law to cause existing gun owners
to decide not to kill with their weapons.  Finding the gaping hole in
this argument is left as an exercise to the reader.  (Hint: gun
control did not apply only to new gun purchases.)

>>"The world is complicated, so simple models can't fit the data".
>>Ahem.  The simple model DOES fit the data.  Huff and puff all you
>>want, you can't get away from that fact.

> "Ahem" indeed.  The data isn't complete, so its "fit" is basically
> meaningless.  For one, the step model explanation is inappropriate
> without "nothing else changed" data, which hasn't been presented.

Gee, Andy what has changed your mind?  On Wed, 18 Dec 1991 20:38:12
GMT, andy@SAIL.Stanford.EDU (Andy Freeman) said: 
> Why doesn't Lambert tell us about pre-control crime and murder rates
> and trends in Oz and compare them to post-control rates and trends?
> If gun control actually worked in Oz, the introduction of controls was
> associated with a good change in the rate trend.  Could it be that
> there wasn't a good change associated with the introduction of
> controls?

I provide the data that Andy requested and now he tells us that it is
meaningless unless I provide data about "everything else" that
happened.  If you felt that the data you asked for was meaningless,
why did you ask for it?  Could it be that you consider data to be
"meaningless" only if it does not support your beliefs?

>>>>> On 4 Dec 91 00:00:31 GMT, andy@SAIL.Stanford.EDU (Andy Freeman) said:

> BTW - If Lambert has evidence of my bias, he's invited to present it.

You reject data that you asked for, and which does not support your
position, as "meaningless".

Faith is such a comfort.

Tim
Newsgroups: talk.politics.guns