Interdisciplinary Urban Sociology of Municipal Rental Deposit Escrow Registration Deadlines and Informal Landlord Withdrawal from Tenancy Agreements in Lagos's Low-Income Compounds: A Bunching Estimation of Registration Thresholds

Municipal rental deposit escrow registration in Lagos creates a sharp administrative threshold: deposits above a stated value must be lodged with the municipality by a fixed deadline, while deposits below it need not be. the present analysis treats that threshold as a bunching environment and asks what a before–after–control–impact (BACI) design can and cannot identify about informal landlord withdrawal from tenancy agreements when registration deadlines bind. Because no observational data are used or claimed, the contribution is methodological and conceptual: the paper specifies the withdrawal mechanism, formalises the bunching estimand, and characterises the operating characteristics of the BACI estimator under a declared variance structure with an intraclass correlation of 0.64, a between-cluster standard deviation of 6.0 and a residual standard deviation of 4.5. Power was estimated across 2000 replications per design cell for cluster counts of 8, 16, 24 and 32 and effects of 3, 5 and 8 percentage points. Fifty-four clusters are required for 80 per cent power at a 5-percentage-point effect. Deadline-induced bunching is a threat to the parallel-trends assumption rather than a nuisance to be averaged away, and it derives the conditions under which a BACI contrast remains interpretable.