From: watt-alan@net.yale.edu (Alan Watt)
Subject: Re: NSW homicides
Originator: swatt@mickey.CS.Yale.Edu
Organization: Yale University, Computing & Information Systems
Date: Tue, 13 Oct 1992 15:57:10 GMT


In article <1992Oct10.190132.772@ucsu.Colorado.EDU>, fcrary@ucsu.Colorado.EDU (Frank Crary) writes:
|> In article <1992Oct9.145803.6337@csi.jpl.nasa.gov> mwette@csi.jpl.nasa.gov (Matt Wette) writes:
|> >My impression is that Tim Lambert proposed a correlation between crime
|> >statistics and gun control in two sets of successive years.  I'm
|> >guessing that Andy Freeman then made the argument was then that these
|> >aren't necessarily correlated (which is true -- any number of other
|> >events could have led to the change).  He then proposed some other
|> >model maybe?
|> 
|> Several of us proposed a different model: A gradual, decade-long decline, 
|> due to other factors, begining several years before the passage of the
|> gun control law. The chi-square fits for Lambert's sudden change model,
|> and our gradual decline model were roughly the same as I recall, though there
|> was _massive_ variation depending on the time interval considered.
|> The argument not is over the number a parameters used: Lambert claims the
|> gradual decline model uses more parameters than his, and therefore
|> his model is superious, despite similar chi-square values. 
|> 
|>                                               Frank Crary
|>                                               CU Boulder


I'll admit up-front I neither have a formal degree in statistics, nor do
I use them regularly.  But I gather the original study was of the decline
in homicide rates in NSW starting shortly after end of WWI.  I assume
(unlike some of the junk studies regarding Washington D.C.), that these
rates were per-100,000 population, or some similar unit.

However, what effect did WW-I have on the age-distribution of the population?
I would expect the percentage of 18-25 year-olds in the general population
to be reduced due to war casualties.  In the U.S., this is the age group
which accounts for most of the violent crime.

Also, I don't know how Austrailian military forces are organized, but in
G.B., they are (or were at the time) grouped in units by geographical
area.  That is, each regiment would be composed of people from the same
place.  A unit which got wiped out therefore consisted of a lot of
neighbors and relatives.  If the war casualties did have a significant
effect on the age distribution of the population most likely to commit
violent crime, it would also tend to have a very high regional variation,
or at least higher than the same casualty rates would have on the U.S.,
which deliberately homoginizes its forces.

I also don't know the Australian casualties in WW-I; I do know casualties
in Scotland were quite high.  In the War Memorial building in Edinburgh,
the book for one regiment listed two and a half pages of Watts; another
regiment listed almost two pages worth.  Watt is not a terribly common
name even in Scotland.  And Scotland was not a very populated country
either.  I suspect the supply of young men after 1918 was drastically
reduced in Scotland, and not a few of the remaining either left or were
evicted during the hard times which followed.  Not a whole lot of people
left to be trouble-makers.
-- 
  Alan S. Watt
  Yale University			Computing and Information Systems
  Box 2112 Yale Station			(203) 432-6602
  New Haven, CT  06520-2112		Watt-Alan@Yale.Edu
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