A Meta-Analysis of the Impact of External Interventions on Conflict Intensity: Navigating Heterogeneity and Unveiling Genuine Effects

We investigate 833 reported estimates detailing the impact of external interventions aimed at alleviating civil war on conflict intensity. This investigation encompasses 34 studies conducted between 1996 and 2020, primarily focusing on African countries. While the average reported effect is both negative and statistically significant, our analysis reveals substantial divergence in the results. We apply meta-regression analysis to examine the sources of this heterogeneity. Our main findings are as follows. First, differences in data, intervention targets, conflict intensity measures, and the publication year of the primary studies account for the observed heterogeneity in reported estimates. Second, we find no evidence of publication selection bias that aligns with prior beliefs, theoretical expectations, or statistical significance. Third, after considering potential sources of heterogeneity and publication bias, the overall genuine effect of external intervention remains negative and statistically significant. This implies that external intervention efforts do mitigate conflict intensity, albeit with a small magnitude of the statistical significance coefficient. For policy purposes, external interventions are likely to have a modest effect. Plain language summary Do external interventions restrain conflict intensity? A meta-analysis of evidence on heterogeneity and genuine effects We looked at whether external interventions affect the intensity of conflicts predominantly in African countries for studies published from 1996 to 2020. It seems like external interventions usually reduce conflict intensity, but the results from different studies vary a lot. We studied 833 reported results from 34 studies to understand why. Overall, the average effect of these interventions is negative, meaning they do reduce conflict, but the results differ because of things like different data, targets of the interventions, and how conflict intensity is measured. We also found that there’s no publication selection bias in how studies are published. After considering all these factors, we still see a statistically significant negative effect, meaning external interventions do help reduce conflict intensity, but the impact is modest.