Municipal water-tariff block pricing and informal settlement yard-tap resale margins in Kenyan urban wards: a regression-discontinuity estimation of consumption-block thresholds

Because no observational data are available for this run, the paper is a methodological and design study rather than an empirical estimate: it specifies the tariff-block mechanism, formalises the resale-margin quantity that a discontinuity would have to move, and characterises the operating characteristics of a before-after-control-impact estimator under a declared variance structure. The design parameters are eight, sixteen, twenty-four and thirty-two clusters; effects of three, five and eight percentage points; and two thousand replications per cell. With a between-cluster standard deviation of 6.0, a residual standard deviation of 4.5 and an intraclass correlation of 0.64, the design requires fifty-four clusters to detect a five-percentage-point effect at eighty per cent power. The block-threshold discontinuity is a credible identification strategy only when the running variable is measured at the yard-tap rather than the ward level, and it sets out the conditions under which the estimator would recover a resale-margin effect rather than a tariff-schedule artefact.