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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