walkthrough-both-bandings-and-rurality

Date: 2026-09-18. Status: implemented.

Decision. The walkthrough returns the Scottish Government unweighted quintile and decile beside the PHS population-weighted ones, and the 6-fold and 8-fold urban-rural codes with a label for the 6-fold. The unweighted bands come from the record that supplied the data zone; the rurality comes from the matched record itself, which is what the generated query does, so a large user reports its own point location rather than that of the small-user postcode it links to. Its demo input became three rows, and the equivalence test now compares these four columns too.

Reason. A reader validating the logic has to see that the same rank produces two different bands: PHS splits so each band holds a fifth or a tenth of the population, the Scottish Government splits the data zones themselves, and a report that mixes them is wrong in a way nothing else catches. Rurality is routinely crossed with deprivation, and holding it next to the band makes its one limitation visible: the directory carries a single 2022 classification, so a historical address is described by today's categories even though its data zone and SIMD are read at the right vintage.

Evidence. Of 162,049 current postcodes with a 2020v2 band, 5,615 fall in a different quintile and 12,216 in a different decile under the two bandings. The demo's second row, AB21 0SB on 1 June 2015, is quintile 3 weighted by population and 4 by data zone, decile 6 against 7. The 6-fold labels are the Scottish Government classification and nest exactly as the two columns do in the data: code 4 covers 8-fold 4 and 5, code 5 covers 6, code 6 covers 7 and 8. The NRS dictionary documents only the ranges, 1 to 6 and 1 to 8.