Homicides in states with a change in the law, United States, 1979–98*
| “Shall issue” law | Minimum age of 21 years for purchase | Minimum age of 21 years for possession | One gun a month | Junk gun ban | |
|---|---|---|---|---|---|
| *For states amending or implementing the law during the period 1979–98. | |||||
| †Mean count per 100 000 person years for states in which law was implemented during study period. | |||||
| ‡p Value for test of homogeneity. | |||||
| §Percentage of total variation in RR due to between state heterogeneity. | |||||
| ¶Regression derived rate ratio of mortality rate with the law to mortality rate without the law, adjusted for all confounders. | |||||
| NA, not applicable because there was only one state with this law. | |||||
| Firearm homicides | |||||
| Rate† with law | 5.00 | 4.91 | 4.61 | 6.13 | 8.83 |
| Rate† without law | 5.90 | 3.10 | 3.86 | 6.55 | 6.12 |
| Range of rate ratios | 0.53–2.71 | 0.60–1.64 | 0.93–1.72 | 1.01–1.07 | NA |
| p Value‡ | <0.001 | 0.38 | 0.16 | 0.76 | NA |
| I2§ | 86% | 7% | 39% | 0% | NA |
| RR¶ | 1.11 | 0.98 | 1.06 | 1.02 | 0.94 |
| 95% CI | 0.99–1.24 | 0.91–1.06 | 0.88–1.27 | 0.89–1.17 | 0.73–1.19 |
| All homicides | |||||
| Rate† with law | 7.50 | 7.70 | 6.99 | 8.49 | 12.2 |
| Rate† without law | 8.99 | 5.51 | 6.48 | 9.74 | 9.71 |
| Range of rate ratios | 0.58–2.10 | 0.85–1.37 | 0.89–1.43 | 0.99–1.09 | NA |
| p Value‡ | <0.001 | 0.55 | 0.12 | 0.56 | NA |
| I2§ | 85% | 0% | 46% | 0% | NA |
| RR¶ | 1.07 | 1.00 | 1.02 | 1.00 | 0.94 |
| 95% CI | 0.98–1.17 | 0.94–1.05 | 0.89–1.18 | 0.90–1.12 | 0.78–1.14 |