Interdisciplinary Urban Sociology of Municipal Fire Safety Certificate Renewal Fees and Small Workshop Closure in Nairobi's Industrial Areas: A Bunching Estimation of Fee Thresholds

Municipal fire safety certificate renewal fees are typically analysed as a revenue instrument or a compliance cost, but their threshold structure may also reorganise the small workshop population in ways that neither fiscal nor regulatory accounts anticipate. Because no observational data are available for the present analysis, the paper 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 an intraclass correlation of 0.64. 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 design requires 54 clusters to detect a 5 percentage point effect at 80 per cent power. Bunching estimation at fee thresholds offers a more credible identification strategy for closure effects than aggregate closure rates, and it specifies the sociological mechanisms — liquidity constraints, licensing visibility and neighbourhood network effects — that make threshold responses plausible. The contribution is a transferable design template for studying how municipal fee schedules shape small-firm survival in African industrial districts.