TABLE 1—

Difference-in-Difference Analysis of Suicide Mortality by Gender: Australia, 1978–2015

Variable	RR (95% CI)
Women
Age group, y
15–29	1 (Ref)
30–44	1.33 (1.27, 1.38)
45–59	1.42 (1.35, 1.49)
≥ 60	1.15 (1.10, 1.20)
Method
Nonfirearm	1 (Ref)
Firearm	0.19 (0.15, 0.24)
Year	0.987 (0.983, 0.992)
Period
Before NFA	1 (Ref)
After NFA	0.72 (0.62, 0.84)
Firearm–year interaction
Nonfirearm	1 (Ref)
Firearm	0.952 (0.938, 0.967)
NFA–year interaction
Before NFA	1 (Ref)
After NFA	1.016 (1.010, 1.021)
NFA–method interaction
Before NFA–nonfirearm	1 (Ref)
Before NFA–firearm	1 (Ref)
After NFA–nonfirearm	1 (Ref)
After NFA–firearm	1.54 (0.63, 3.77)
NFA–method–year interaction (DiD term)
Before NFA–nonfirearm	1 (Ref)
Before NFA–firearm	1 (Ref)
After NFA–nonfirearm	1 (Ref)
After NFA–firearm	0.974 (0.955, 1.004)
Men
Age group, y
15–29	1 (Ref)
30–44	1.19 (1.16, 1.21)
45–59	1.06 (1.03, 1.08)
≥ 60	1.02 (0.99, 1.04)
Method
Nonfirearm	1 (Ref)
Firearm	1.25 (1.16, 1.35)
Year	1.032 (1.029, 1.035)
NFA period
Before NFA	1 (Ref)
After NFA	3.15 (2.89, 3.44)
Firearm–year interaction
Nonfirearm	1 (Ref)
Firearm	0.942 (0.938, 0.947)
NFA–year interaction
Before NFA	1 (Ref)
After NFA	0.956 (0.952, 0.959)
NFA–method interaction
Before NFA–nonfirearm	1 (Ref)
Before NFA–firearm	1 (Ref)
After NFA–nonfirearm	1 (Ref)
After NFA–firearm	0.31 (0.24, 0.39)
NFA–method–year interaction (DiD term)
Before NFA–nonfirearm	1 (Ref)
Before NFA–firearm	1 (Ref)
After NFA–nonfirearm	1 (Ref)
After NFA–firearm	1.027 (1.019, 1.036)

Note. CI = confidence interval; DiD = difference in difference; NFA = Australian National Firearms Agreement; RR = rate ratio.