TABLE 2—
Results from Poisson Regressions: South Dakota’s 24/7 Sobriety Project, 2001–2010
| DUI-1 (n = 7800), IRR (95% CI) | Repeat DUI (n = 7920), IRR (95% CI) | Domestic Violence (n = 7560), IRR (95% CI) | Traffic Crashes (n = 5544), IRR (95% CI) | Traffic Crashes, Men Aged 18–40 Years (n = 5544), IRR (95% CI) | |
| 24/7 implemented | 1.062 (0.955, 1.181) | 0.883* (0.794, 0.983) | 0.905* (0.825, 0.993) | 0.980 (0.941, 1.021) | 0.956 (0.909, 1.006) |
| Populationa | 1.607 (0.745, 3.466) | 10.522* (1.343, 82.46) | 2.327* (1.069, 5.068) | 1.188 (0.838, 1.683) | 1.625** (1.184, 2.231) |
| Percentage White | 10.672 (0.002, 45 568) | < 0.001* (< 0.001, 0.904) | < 0.001 * (< 0.001, 0.743) | 0.010 (< 0.001, 4.440) | 0.009 (< 0.001, 5.234) |
| Men aged 18–40 y share of population | < 0.001* (< 0.001, 0.654) | < 0.001* (< 0.001, 0.185) | < 0.001 (< 0.001, 18.344) | 1.269 (0.003, 570.135) | 7.358 (0.015, 3515.884) |
| Unemployment rate | 0.981 (0.944, 1.020) | 1.005 (0.975, 1.036) | 0.949* (0.902, 0.998) | 0.965 (0.930, 1.001) | 0.967 (0.935, 1.000) |
| Police officers per capitab | 1.008 (0.991, 1.026) | 1.002 (0.984, 1.020) | 1.004 (0.978, 1.030) | 1.020** (1.005, 1.036) | 1.018* (1.001, 1.035) |
| VMT per capitac | 1.056 (0.887, 1.257) | 1.076 (0.698, 1.661) | 1.046 (0.952, 1.149) | 1.007 (0.916, 1.107) | |
| Bars per capitab | 1.002 (0.977, 1.027) | 0.977 (0.939, 1.017) | 1.001 (0.975, 1.029) | 0.997 (0.989, 1.005) | 1.000 (0.990, 1.010) |
| Package stores per capitab | 1.056* (1.002, 1.114) | 0.976 (0.913, 1.044) | 1.005 (0.956, 1.055) | 1.000 (0.978, 1.022) | 1.002 (0.980, 1.025) |
| Snowfalld | 0.942 (0.725, 1.224) | 0.903 (0.677, 1.204) | 0.944 (0.843, 1.057) | 1.251* (1.048, 1.493) | 1.560*** (1.338, 1.820) |
| Sturgis Rally | 2.854 (0.934, 8.723) | 1.477*** (1.330, 1.641) | 1.240* (1.013, 1.519) | 1.642*** (1.293, 2.086) | 1.485** (1.154, 1.910) |
| College in session | 1.026 (0.677, 1.555) | 0.970 (0.812, 1.159) | 0.920 (0.829, 1.021) | 1.071 (0.922, 1.244) | 1.153* (1.003, 1.327) |
| DUI-1 polynomial | |||||
| First degree | 1.241*** (1.181, 1.304) | ||||
| Second degree | 0.873*** (0.838, 0.910) | ||||
| Third degree | 1.108*** (1.068, 1.148) | ||||
| Fourth degree | 0.972 (0.940, 1.004) | ||||
| Fifth degree | 1.000 (0.982, 1.018) |
Note. CI = confidence interval; DUI = driving while under the influence of alcohol; DUI-1 = first-time DUI; IRR = incidence rate ratio; VMT = vehicle miles traveled. All models included county fixed effects and year–month fixed effects. Ninety-five percent confidence intervals estimated by using robust standard errors clustered at the county level in parentheses. The full sample size for repeat DUI arrests is 7920 based on a full 10-year county–month panel (66 counties × 10 y × 12 mo). The sample sizes for DUI-1 and domestic violence arrests are smaller because some counties reported no arrests for certain offenses to the state Department of Criminal Investigation over the entire time period. For DUI-1, this includes Shannon County whereas for domestic violence this includes Shannon, Dewey, and McPherson counties. Sample sizes for the crash models were 5544 because we only had data for 2004 through 2010 (66 counties × 7 y × 12 mo).
Natural log of monthly linear interpolation of population.
Per capita measure based on rate per 10 000 people.
VMT are based on annualized rate; miles in 10 000s.
Natural log of average monthly snowfall in inches.
*P < .05; **P < .01; ***P < .001.