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Table 2 Zero-inflated negative binomial model describing the relationship between a state’s total number of firearm laws and number of states to which it is the source of 100 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 −1.15 (−1.64, −0.66)*** 0.32
Year 0.11 (0.08, 0.14)*** 1.11
Poverty rate 0.13 (0.04, 0.22)** 1.14
Density −0.15 (−0.27, −0.03)* 0.86
Area 0.90 (0.74, 1.06)*** 2.46
Firearm ownership −0.46 (−0.58, −0.35)*** 0.63
Number of laws −0.55 (−0.71, − 0.27)*** 0.58
Census division
 New England Ref  
 Mid-Atlantic 2.41 (1.77, 3.05)*** 11.13
 East North Central 1.88 (1.37, 2.39)*** 6.54
 West North Central 0.28 (−0.31, 0.88) 1.33
 South Atlantic 2.39 (1.91, 2.87)*** 10.92
 East South Central 1.69 (1.17, 2.20)*** 5.40
 West South Central 0.63 (0.03, 1.23)* 1.87
 Mountain 0.16 (−0.36, 0.69) 1.18
Pacific 1.83 (1.34, 2.32)*** 6.26
Zero-inflation model
Variable b (95% CI) Adjusted Odds Ratio
Intercept −2.42 (−3.01, −1.83)*** 0.09
  1. * p < 0.05, ** p < 0.01, *** p < 0.001