Municipal street-lighting metering and informal night-market vendor revenue volatility in Ghanaian district assemblies: a difference-in-differences estimation of separately-metered feeder thresholds

No observational data are used or claimed. The analysis characterises the operating characteristics of the BACI estimator under a declared variance structure with a between-cluster standard deviation of 6.0, a residual standard deviation of 4.5, and an intraclass correlation of 0.640. Power was estimated across 2000 design cells defined by cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The results indicate that 54 clusters are required to detect a 5-percentage-point effect at 80 per cent power. The BACI design is defensible for this application only when the cluster count exceeds a threshold that the intraclass correlation makes substantially higher than conventional power calculations assume. The contribution is a design-based clarification of the conditions under which separately-metered feeder thresholds can be credibly evaluated, and a demonstration that the intraclass correlation of 0.64 imposes a sample-size burden that most district-assembly evaluations do not meet.