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Table 4 Zero-inflated negative binomial model describing the relationship between a state’s total number of firearm laws and number of other states for which it is the source of 50 or more crime-related firearms in a given year, adjusting for state-level characteristics, 2010–2017

From: Firearm laws and the network of firearm movement among US states

Negative binomial model
Variable b (95% CI) Incidence Rate Ratio
Intercept −0.62 (−0.96, −0.28)*** 0.54
Year 0.09 (0.06, 0.13)*** 1.10
Poverty rate 0.33 (0.20, 0.46)*** 1.39
Density −0.08 (−0.19, 0.04) 0.92
Area 0.21 (0.08, 0.35)** 1.24
Firearm ownership −0.35 (−0.46, −0.25)*** 0.70
Number of laws −0.07 (−0.21, 0.08) 0.94
Census division
 New England Ref  
 Mid-Atlantic 1.96 (1.21, 2.71)*** 7.08
 East North Central 2.19 (1.84, 2.53)*** 8.93
 West North Central 0.90 (0.47,1.33)*** 2.46
 South Atlantic 2.28 (1.89, 2.66)*** 9.74
 East South Central 2.03 (1.62, 2.43)*** 7.59
 West South Central 1.60 (1.15, 2.05)*** 4.97
 Mountain 0.95 (0.56, 1.34)*** 2.59
 Pacific 1.19 (0.77, 1.61)*** 3.29
Zero-inflation model
Variable b (95% CI) Adjusted Odds Ratio
Intercept −10.05 (−1027.36, 1007.26) 4.32 × 10−05
  1. * p < 0.05, ** p < 0.01, *** p < 0.001