Effects of gun control in Australia

In a previous posting I observed that the homicide rate in New South
Wales fell dramatically following the introduction of gun controls in
1920.

Here, again, is the graph showing the homicide rate in NSW from 1900-1977.
(Vertical scale is homicide rate per 100 000 population)

3      *  
2.8
2.6        
*
2.4 * 2.2 *
2.0 * * * 1.8 * * * * *
*
1.6 *
* * * 1.4 *
* *
*
* * 1.2 * * * *
1.0 * *
0.8 * 0 1 2 3 4 5 6 7 012345678901234567890123456789012345678901234567890123456789012345678901234567

It is quite possible that the decline in the homicide rate was caused
by factors other than gun control (e.g changing demographics, improved
law enforcement, better birth control methods). To test this
hypothesis, we need a control, an adjacent state that did not
introduce gun control in 1920, to see if that state also experienced a
similar decline after 1920. Victoria introduced gun controls into
1921 and Queensland in 1927, so I decided to look at Queensland.

I couldn't find any data for the homicide rate in Queensland prior to
72. I was able to find the numbers of people charged with
manslaughter and murder from 1900-1977. Adding these and dividing by
the population each year gives the homicide charge rate per 100 000
people, which is the vertical scale on the following graph.

9.0 *
8.5
8.0
7.5  * *  *
7.0*  *    *
6.5     *
6.0      *                    *
5.5                  *        |                                      *
5.0                 *      * *|                                *    * *
4.5         **  *             |                 *               * **
4.0           *  ***  * *     |*            *  * *  *  *     **  *     * *   *
3.5                    *  * * | *  *     *** **   *     *  **              **  *
3.0            *       | *    |                      *   **             *     * *
2.5                    |      |  ** *** *          *  *                   *
2.0                    |      |
1.5                    |      |        *
   0         1         2      |  3         4         5         6         7
   012345678901234567890123456789012345678901234567890123456789012345678901234567

The rate did not drop after 1920, but did drop after 1927 (when gun
controls were introduced).

Here is the average homicide charge rate in Queensland for 7 year
periods:

Years average rate
00-06 7.2
07-13 5.0
14-20 4.2
21-27 4.3
28-34 3.0
35-41 2.9
42-48 3.6
49-55 3.2
56-62 4.1
63-69 4.5
70-76 3.4

The rate for 21-27 was the same as the previous 7 year period, but it
dropped significantly in the next seven years.

Tags

More like this

Could the changes be caused by noise? This calls for a t test, to see if the average homicide rate changed. Andy Freeman said: There's an interesting thing about averages. If you take the average of a declining series and compare it to the end point, you find that the average is, not surprisingly…
Frank Crary said (referring to changes in homicide rate in NSW and Qld): The sharp drop you claim to see, is (in my opinion) not significant compared to the background variations. While this may have been real effect of gun control laws, in is at least as likely that it is a coincidence. Could the…
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…
What on earth do you mean by 'the "nothing else happened" parameter"? Andy Freeman said: 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…