Table 1.
Negative binomial regression models for total number of violent events per grid cell, 1991–2009
| a) GLM socioeconomic, physical, and climate |
b) SPI6 binary dry (≤−1 σ) |
c) SPI6 binary wet (≥1 σ) |
d) TI6 binary hot (≥1 σ) |
e) TI6 binary cold (≤−1 σ) |
f) GAM splines |
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| Estimate | z value | Estimate | z value | Estimate | z value | Estimate | z value | Estimate | z value | Estimate | z value | |
| Intercept | −8.196 | −5.995* | −8.173 | −5.982* | −8.235 | −6.017* | −8.216 | −6.011* | −8.228 | −6.031* | −8.292 | −6.029* |
| Space–time lag | 0.524 | 14.917* | 0.525 | 14.993* | 0.526 | 14.961* | 0.530 | 14.857* | 0.532 | 14.822* | 0.512 | 14.789* |
| Precipitation (SPI6) | −0.048 | −1.558 | −0.053 | −1.730 | −0.057 | −1.832 | ||||||
| SPI6 dry | −0.044 | −0.566 | ||||||||||
| SPI6 wet | −0.205 | −2.231† | ||||||||||
| Spline (SPI6) | P value | 0.000* | ||||||||||
| Temperature (TI6) | 0.078 | 1.545 | 0.089 | 1.779 | 0.081 | 1.613 | ||||||
| TI6 hot | 0.061 | 0.873 | ||||||||||
| TI6 cold | 0.021 | 0.113 | ||||||||||
| Spline (TI6) | P value | 0.000* | ||||||||||
| Ethnic leadership | −0.334 | −1.583 | −0.340 | −1.604 | −0.337 | −1.599 | −0.323 | −1.541 | −0.314 | −1.492 | −0.332 | −1.572 |
| Distance to border (ln) | −0.420 | −4.906* | −0.419 | −4.888* | −0.419 | −4.880* | −0.422 | −4.923* | −0.424 | −4.938* | −0.417 | −4.843* |
| Capital city grid cell | 1.636 | 5.666* | 1.634 | 5.652* | 1.627 | 5.651* | 1.635 | 5.676* | 1.632 | 5.672* | 1.625 | 5.655* |
| Population (ln) | 0.495 | 7.457* | 0.498 | 7.490* | 0.499 | 7.509* | 0.494 | 7.453* | 0.494 | 7.448* | 0.502 | 7.551* |
| Wellbeing (IMR lag) | 0.010 | 1.604 | 0.010 | 1.554 | 0.010 | 1.568 | 0.010 | 1.647 | 0.010 | 1.670 | 0.010 | 1.600 |
| Political rights (lag) | 0.087 | 1.766 | 0.085 | 1.731 | 0.091 | 1.858 | 0.089 | 1.810 | 0.090 | 1.833 | 0.092 | 1.896 |
| Presidential election buffer | 0.303 | 2.541† | 0.287 | 2.414† | 0.306 | 2.560† | 0.308 | 2.619* | 0.310 | 2.653* | 0.325 | 2.715* |
| Grassland (%) | 0.020 | 4.131* | 0.020 | 4.126* | 0.020 | 4.112* | 0.020 | 4.148* | 0.020 | 4.157* | 0.020 | 4.088* |
| Distance to road (ln) | −0.400 | −3.151* | −0.400 | −3.146* | −0.400 | −3.141* | −0.401 | −3.150* | −0.401 | −3.156* | −0.388 | −3.084* |
| Crop production index (pct. Δ) | −0.004 | −1.447 | −0.004 | −1.551 | −0.004 | −1.507 | −0.004 | −1.476 | −0.004 | −1.473 | −0.004 | −1.601 |
| VCI (lag) | −0.002 | −0.956 | −0.002 | −0.971 | −0.001 | −0.909 | −0.001 | −0.893 | −0.001 | −0.877 | −0.002 | −0.955 |
| Log-likelihood | −25,150.6 | −25,153.0 | −25,146.1 | −25,153.9 | −25,155.0 | −25,112.0 | ||||||
| AIC | 50,395.1 | 50,399.9 | 50,386.3 | 50,401.9 | 50,404.0 | 50,331.7 | ||||||
| AUC | 0.849 | 0.849 | 0.849 | 0.849 | 0.849 | 0.850 | ||||||
Number of observations for all models is 91,656 grid months. Binary models b–d use precipitation and temperature anomalies of beyond 1 SD (σ) of the long-term mean to define binary variable. All models are estimated with year and country fixed effects (not shown). AIC, Akaike information criterion; IMR, infant mortality rate; VCI, vegetation condition index.
*P < 0.01 using grid-clustered SEs.
†P < 0.05 using grid-clustered SEs.