Regarding the reduction in gun homicides and suicides in Australia since the gun law changes.
From:
https://jamanetwork.com/journals/jama/fullarticle/2530362
Total Firearm and Nonfirearm Suicide and Homicide Deaths
Overall suicide and homicide deaths from firearm involvement for the period 1979 to 2013 are reported in the
Figure, panels G, H, and I. An increasing trend in total deaths (total homicide and suicide deaths) in the years 1979-1996 was followed by a decreasing trend in 1997-2013 (
Figure, panel G), resulting in a negative ratio of annual trends (RT = 0.975; 95% CI, 0.968-0.983) but not a negative step change (RL = 0.991; 95% CI, 0.918-1.071) (
Table 3). Although total firearm deaths were already declining in 1979-1996, the trend accelerated in 1997-2013 (
Figure, H), resulting in a negative ratio of trends (RT = 0.981; 95% CI, 0.968-0.993) as well as a negative step change (RL = 0.669; 95% CI, 0.589-0.760) (
Table 3). The annual rate of total nonfirearm deaths was increasing in 1979-1996 but declined in the period 1997-2013 (
Figure, I), although only after an initial positive step change. This resulted in a negative ratio of trends (RT = 0.966; 95% CI, 0.958-0.973) but a nonsignificant step change (RL = 1.054; 95% CI, 0.974-1.141) (
Table 3).
Total Suicide Deaths
Total (firearm + nonfirearm) suicide annual death rates had been increasing by a mean of 1.0% per year before the introduction of the gun control laws, for an overall mean of 12.3 (95% CI, 11.9-12.7) per 100 000 population, but declined by a mean of 1.5% per year after the introduction of the 1996 gun laws (
Table 3), for an overall mean of 11.7 (95% CI, 11.1-12.3) per 100 000 (
Figure, A). The ratio of the prelaw-to-postlaw trends was statistically significant (RT = 0.975; 95% CI, 0.968-0.982), but the step change was not statistically significant (RL = 1.004; 95% CI, 0.931-1.083) (
Table 3).
Total Homicide Deaths
Total (firearm + nonfirearm) homicide annual death rates had been decreasing by a mean of 0.3% per year before the introduction of the gun control laws for an overall mean of 1.93 (95% CI, 1.86-2.00) per 100 000 population, but this decline accelerated to a mean of 3.1% per year after the introduction of the 1996 gun laws (
Table 3) for an overall mean of 1.29 (95% CI, 1.17-1.43) per 100 000 (
Figure, D). The ratio of the prelaw-to-postlaw trends was statistically significant (RT = 0.972; 95% CI, 0.958-0.986), but there was no significant step change (RL = 0.908; 95% CI, 0.784-1.050) (
Table 3).
Firearm Suicides
Firearm suicides represent the largest component cause of total intentional firearm deaths in Australia (83.9% between 1979-2013) (
Table 2). In the 18 years 1979-1996, the mean annual rate of firearm suicide was 3.0 (95% CI, 2.8-3.3) per 100 000 population. In the 17 years following the announcement of the new gun laws, this declined to a mean of 0.99 (95% CI, 0.87-1.13) per 100 000. The rate of firearm suicide was declining by an average of 3% per year before gun law reforms, and this decline increased to 4.8% per year after the introduction of revised gun laws (
Figure, B;
Table 3). The ratio of trend estimates was 0.981 (95% CI, 0.970-0.993). There was evidence of a step change in the level of firearm-related suicide deaths (RL = 0.652; 95% CI, 0.582-0.731) (
Table 3).
Firearm Homicides
In the 18 years 1979-1996, the mean annual rate of firearm homicide was 0.57 (95% CI, 0.51-0.63) per 100 000 population. In the 17 years following the announcement of the new gun laws, this rate declined to 0.20 (95% CI, 0.17-0.25) per 100 000 persons. The rate of firearm homicide was declining by a mean of 3% per year; this rate of decline accelerated to a mean of 5.5% per year after the introduction of new gun laws, although this change was not statistically significant (RT = 0.975; 95% CI, 0.949-1.001) (
Figure, E;
Table 3). The ratio of trends in annual death rate was slightly reduced when the mass homicides that occurred during 1979-1996 were removed (RT = 0.985; 95% CI, 0.962-1.009). In addition, there was a nonsignificant negative step change (RL = 0.769; 95% CI, 0.590-1.004) (
Table 3).
Nonfirearm Suicides
The rate of total nonfirearm suicides increased by a mean of 2.3% per year before the introduction of the gun control laws, for an overall mean of 9.2 (95% CI, 8.7-9.8) per 100 000 population, but declined by a mean of 1.2% per year after the introduction of the 1996 gun laws, for an overall mean of 10.7 (95% CI, 10.3-11.2) per 100 000 (
Figure, C;
Table 3). The ratio of the prelaw-to-postlaw trends was statistically significant (RT = 0.965; 95% CI, 0.958-0.973), but there was no statistically significant step change (RL = 1.070; 95% CI, 0.988-1.159) (
Table 3). The data do not support any suicide method substitution hypothesis.
Nonfirearm Homicides
The rate of total nonfirearm homicides increased by a mean of 0.9% per year before the introduction of gun control laws, for an overall mean of 1.36 (95% CI, 1.29-1.44) per 100 000 population, and decreased by a mean of 2.6% per year after the introduction of the new gun laws to an overall mean of 1.09 (95% CI, 1.00-1.19) per 100 000 (
Figure, F;
Table 3). The ratio of the prelaw-to-postlaw trends was statistically significantly different (RT = 0.965; 95% CI, 0.950-0.981), but there was no statistically significant step change (RL = 0.941; 95% CI, 0.803-1.103) (
Table 3). The data do not support any homicide method substitution hypothesis.
Discussion
In the 20 years (May 1996-May 2016) since the gun law reforms and buyback programs, no mass shootings (ie, ≥5 victims) have occurred in Australia. In addition, there was a more rapid decline in total firearm deaths after gun law reforms (1997-2013) compared with before gun law reforms (1979-1996). The prelaw reform decline in firearm suicides increased significantly after the reforms, and the decline in firearm homicides also increased, although this did not reach statistical significance. Total suicides (all methods including firearms) increased by a mean of 1% per year before the introduction of the 1996 gun laws and decreased by a mean of 1.5% per year after the introduction of the new gun laws. Although the annual trend in total homicide was slightly declining in 1979-1996 by less than 1%, this trend accelerated to a 3.1% decline after the introduction of gun control laws (1997-2013). The ratio of the prelaw-to-postlaw trends was statistically significant for both total suicide (
P < .001) and total homicide (
P < .001) (
Table 3).