Interdisciplinary Urban Sociology of Municipal Vacant Land Holding Tax Arrears and Smallholder Plot Abandonment in Nairobi's Peri-Urban Fringe: A Bunching Estimation of Arrears Thresholds

Municipal vacant land holding tax arrears in Nairobi's peri-urban fringe are typically treated as a fiscal problem, yet smallholder plot abandonment suggests that arrears thresholds also operate as behavioural tipping points. Because no observational data are available, the study characterises the operating characteristics of a before-after-control-impact design under a declared variance structure: between-cluster standard deviation of 6.0, residual standard deviation of 4.5, and intraclass correlation of 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. The design requires 56 clusters to detect a 5-percentage-point effect at 80% power. Bunching estimation of arrears thresholds is feasible only when the sampling design can distinguish threshold-induced behavioural responses from municipal assessment practices, and it specifies the cluster counts and effect sizes under which that distinction holds. The contribution is a design protocol that integrates sociological theory of abandonment with the statistical power requirements of bunching estimation, offering a template for research on municipal land taxation in African peri-urban contexts.