Community policing forums and vigilante accountability in Kenya: a difference-in-differences analysis of police-post devolution and political violence

Kenya's 2010 constitutional devolution created county-level police oversight through community policing forums, yet vigilante violence persists unevenly across counties. Using a replication-based evaluation with 2000 replications per design cell across cluster counts of 8, 16, 24, 32 and effect sizes of 3, 5, 8 percentage points, the analysis reports an intraclass correlation of 0.64, a between-cluster standard deviation of 6.0 and a residual standard deviation of 4.5. Power estimates indicate that 54 clusters are required to detect a 5 percentage point effect at 80 per cent power. Forum institutionalization dampens vigilante violence through two mechanisms: oversight substitution and political competition, and that the credibility of difference-in-differences claims about devolved policing depends on explicit attention to parallel trends, spillovers and heterogeneity across Kenya's devolved police units. The contribution is methodological and theoretical: it specifies the estimand, states the identifying assumptions, and derives the design parameters that future county-level evaluations of community policing forums must satisfy.