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Table 4 Multilevel Models: Incidence Rate Ratios of Mass Shootings in U.S. Counties

From: Income inequality and mass shootings in the United States

  MSA: Three or More Injuries MSA: Four or More Deaths
MS2000–2009 = ∆ Covariates1990–2000 MS2010–2015 = ∆ Covariates2000–2010 MS2000–2009 = ∆ Covariates1990–2000 MS2010–2015 = ∆ Covariates2000–2010
Adj. IRR (95% CI) Adj. IRR (95% CI) Adj. IRR (95% CI) Adj. IRR (95% CI)
Level 1 = County-Level
 Income inequality 1.47 (1.06, 2.02) 1.50 (1.14, 1.97) 1.54 (1.12, 2.11) 1.63 (1.15, 2.33)
 Poverty rate 0.76 (0.39, 1.47) 2.46 (1.50, 4.03) 0.59 (0.39, 0.90) 2.50 (1.06, 5.91)
 Unemployment rate 0.83 (0.57, 1.22) 1.24 (0.90, 1.69) 0.96 (0.58, 1.59) 0.94 (0.49, 1.78)
 Population density 0.26 (0.03, 2.05) 0.00 (0.00, 0.16) 0.16 (0.01, 1.71) 0.04 (0.00, 3.50)
 Young population 0.74 (0.48, 1.13) 2.98 (1.65, 5.39) 0.83 (0.51, 1.34) 2.54 (1.36, 4.75)
 Minority population 0.87 (0.07, 9.85) 6.58 (2.08, 20.80) 8.61 (1.07, 69.35) 10.43 (2.81, 38.67)
 HS graduation rate 0.19 (0.06, 0.59) 0.99 (0.85, 1.16) 0.19 (0.03, 0.96) 1.00 (0.85, 1.18)
Level 2 = State-Level
 Right to carry laws 4e−32 (3e−65, 50.74) 1.05 (0.39, 2.86) 1e−36 (9e−40, 3e−33) 0.40 (0.00, 48.93)
 Assault rifle ban 1e−29 (3e− 32, 3e−27) 0.84 (0.19, 3.64) 0.16 (0.00, 1972.26) 2.27 (0.95, 5.37)
 Wald Chi-Square 20.17 86.93 22.48 63.22
 County-Decades (N) 3134 3139 3134 3139
  1. Adj. IRR adjusted incidence rate ratio, CI confidence interval. All variables are logged and z-score standardized