Community policing forums and vigilante escalation in Kenya: a difference-in-differences evaluation of political trust erosion and the accountability gap in informal security provision

Community policing forums in Kenya were introduced to bridge the accountability gap between formal police and informal security providers, yet vigilante escalation persists in the very areas where these forums operate. Because no observational data are available for a direct test, the study characterises the operating characteristics of a difference-in-differences design under a declared variance structure (between-cluster SD = 6.0, residual SD = 4.5, intraclass correlation = 0.64). Power was estimated across 2000 design cells for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points.54 clusters are required to detect a 5-percentage-point effect at 80% power, and that the minimum detectable effect declines steeply as cluster count rises. These results establish the feasibility of a rigorous evaluation and specify the accountability mechanisms that such an evaluation must measure.