Urban land-value capture levy schedules and informal trader displacement in Kampala divisions: a regression-discontinuity estimation of assessment-band thresholds

Kampala's division-level land-value capture levy assigns informal traders to assessment bands whose boundaries trigger discrete jumps in payable duty. Regression discontinuity (RD) has been proposed as the natural estimator for the resulting displacement question, but the credibility of any such estimate depends on design operating characteristics that have not been characterised for the clustered, serially repeated assessment structure that Kampala's divisions actually use. Power was estimated across 2000 replications per design cell for cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The analysis indicates that 56 clusters are required to detect a 5-percentage-point displacement effect at 80 per cent power under this variance structure, and that the minimum detectable effect at 80 per cent power falls steeply as cluster count rises from 8 to 32. The results imply that published RD estimates of levy-driven trader displacement in Kampala divisions are likely to be underpowered at the cluster counts typically available, and that the assessment-band threshold should be treated as a design parameter rather than a natural experiment.