# Implementation clarification

Before model estimation, the design audit found 59 strata: 56 have two masked PSUs and three 2011–2012 strata (90, 91, 92) have three. The pre-estimation specification's two-PSU expectation was too restrictive. Retain all published PSUs and require at least two per stratum. The prespecified stratified JKn method supports unequal PSU counts; no model, population, endpoint or uncertainty method is changed. The resulting design has 121 PSUs and 62 design degrees of freedom. The initial failed assertion and diagnostic are retained in Notebook runs.
