Urban development-induced conversion of public transit terminals into commercial plazas and informal trader displacement in Lagos: a difference-in-differences estimation of terminal-redevelopment exposure

The conversion of public transit terminals into commercial plazas in Lagos has been treated in policy debate as a discrete displacement event, yet the quantity that determines whether such an event can be detected at all — the statistical power of the difference-in-differences design used to evaluate it — has not been characterised. Under a declared variance structure with between-cluster standard deviation of 6.0, residual standard deviation of 4.5 and 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 analysis indicates that 54 clusters are required to detect a 5 percentage point displacement effect at 80 per cent power, and that the minimum detectable effect at 80 per cent power falls steeply as cluster count rises from 8 to 32. The contribution is a design specification: it establishes the cluster counts at which terminal-redevelopment evaluations in Lagos can and cannot resolve displacement effects of policy-relevant size, and it reframes the displacement question as one of assignment structure rather than of event magnitude alone.