Table 2.

Bayesian conditional autoregressive Poisson models for counts of firearm homicides; US counties (n = 3,107) from 2000–2014 (t = 15).

	Model 1			Model 2			Model 3
Variable	IRR	(95%	CrI)	IRR	(95%	CrI)	IRR	(95%	CrI)
Within-State Firearm Laws
Laws (count)	0.994	0.993	0.996	0.987	0.984	0.990	0.995	0.992	0.997
Dealer laws (%)							1.000	0.997	1.003
Buyer laws (%)							0.999	0.996	1.002
High risk (%)							0.997	0.994	0.999
Background checks (%)							0.994	0.991	0.997
Possession laws (%)							0.997	0.995	0.999
Concealed carry [reference]
Child access prevention (%)							1.012	1.005	1.020
Domestic Violence (%)							0.999	0.997	1.001
Other laws (%)							1.001	0.999	1.003

Interstate Firearm Laws
Laws (gravity weighted)	0.993	0.990	0.996	0.984	0.979	0.988	0.991	0.986	0.996
Dealer laws (%)							1.011	1.001	1.023
Buyer laws (%)							0.984	0.974	0.992
High risk (%)							0.984	0.977	0.991
Background checks (%)							0.991	0.981	1.000
Possession laws (%)							0.977	0.968	0.985
Concealed carry [reference]
Child access prevention (%)							0.978	0.962	0.992
Domestic Violence (%)							0.998	0.992	1.005
Other laws (%)							0.991	0.983	1.000

Interaction Term
Within-state lawsinterstate laws (100)				1.019	1.013	1.028

County Demographics
Age < 25 [reference]
Age 25–44 (%)	1.010	1.004	1.018	1.011	1.005	1.016	1.006	0.998	1.016
Age 45–64 (%)	1.027	1.021	1.036	1.026	1.019	1.034	1.024	1.015	1.032
Age > 64 (%)	0.994	0.986	1.001	0.995	0.988	1.002	0.992	0.985	1.001
Black (%)	1.032	1.030	1.034	1.032	1.030	1.034	1.032	1.029	1.034
Hispanic (%)	1.013	1.010	1.016	1.013	1.011	1.016	1.014	1.010	1.017
White [reference]
Native (%)	1.015	1.011	1.020	1.015	1.011	1.019	1.014	1.010	1.019
Median household income (2014 US$10,000)	0.906	0.889	0.923	0.902	0.886	0.919	0.901	0.883	0.919
Unemployment (%)	0.988	0.983	0.993	0.988	0.982	0.993	0.989	0.983	0.994

Human Geography
Population in-flow (standardized)	1.009	0.986	1.033	1.002	0.978	1.027	1.015	0.992	1.040
Policy liberalism	1.007	0.971	1.041	0.998	0.964	1.034	1.006	0.966	1.046
Policing expenditure	0.985	0.982	0.988	0.986	0.983	0.989	0.982	0.978	0.985
RUCC Metropolitan [reference]
RUCC Urban	0.906	0.866	0.947	0.904	0.865	0.945	0.901	0.861	0.942
RUCC Rural	0.986	0.916	1.063	0.984	0.913	1.059	0.984	0.913	1.060
Land area (1,000 square kms)	1.006	0.972	1.040	1.004	0.970	1.040	1.012	0.977	1.049

Constants and Error Terms
Constant	1.481	0.996	1.856	1.945	1.513	3.028	5.089	2.017	8.117
Trend	0.990	0.985	0.996	0.991	0.985	0.998	0.991	0.983	1.000
Variance explained by conditional autoregressive random effect (proportion)	0.801	0.709	0.883	0.821	0.732	0.894	0.808	0.709	0.891
Variance explained by state random effect (proportion)	0.007	0.001	0.046	0.007	0.001	0.041	0.080	0.029	0.172

RUCC indicates rural-urban continuum codes. IRR indicates incidence rate ratio. CrI indicates credible interval.