Interdisciplinary Urban Sociology of Municipal Water Kiosk Concession Fee Arrears and Vendor Abandonment in Nairobi's Informal Settlements: A Bunching Estimation of Arrears Thresholds

The problem is framed sociologically: concession fee arrears are not merely a financial residual but a signal of the relational breakdown between municipal authority and informal vendors, and the point at which vendors exit is a threshold of institutional tolerance that has not been formally estimated. Because no observational data are available, the paper specifies a bunching estimator for the arrears distribution and conducts a design and power analysis of the before-after-control-impact variant across a grid of 8, 16, 24 and 32 clusters and effect sizes of 3, 5 and 8 percentage points, with 2000 replications per cell. Under a declared variance structure with between-cluster SD of 6.0, residual SD of 4.5 and intraclass correlation of 0.64, the analysis shows that 54 clusters are required to detect a 5 percentage point effect at 80 per cent power.