simd-domain-ranks

Date: 2026-09-29. Status: implemented.

Decision. Both tables carry the Scottish Government's published SIMD domain ranks for every edition, simd_domain_rank for income, employment, health, education, access, crime and housing, copied exactly as published and appended after every existing column: 41 columns, schemas postcode_simd_wide_v3 and postcode_simd_sspl_v3. 2004 published no crime domain and has no crime column. A new schema type, rank, keeps a value that may end in .5 exactly: float64 in Parquet, one decimal place in the CSV, decimal(6,1) in SQL Server and in the digest, a float in Python, never an integer anywhere. The registry's domains map per government edition is the single statement of which domain exists in which edition; the reader, join, readback, trace, SQL generator and Python API all read it. The SQL output core grows from 41 to 48 columns with seven gov_domain_rank measures; for an edition that did not publish a domain the measure is null and the result is still matched. Python answers an unpublished domain with a null value and a label, not an error. Ranks only: no domain bands or n-tiles. Released as 4.0.0. The published domain bands were added, copied, never derived, by simd-domain-bands on 30 September 2026.

Reason. The HEAL-Scot DRS asks for domain-level data and other projects will. The ranks were already pinned in the Government shapefile attribute tables. They are not whole numbers, and ties are only mostly averaged, so they are copied rather than recomputed, and every layer is held to exactness. The new columns change both schemas, the CSV digest and the loader's expectations, the same reasoning that made the rurality work 3.0.0.

Evidence. 7,796 published domain-rank values end in .5, for example 2020v2 income for S01006523 is 5955.5; of 5,188 tied groups 4,116 carry their average position and 1,072 do not, such as 2009 income 5521 and 2020v2 income 6969. Every value is a whole multiple of 0.5. The saved 2020v2 ranks equal the Government's SIMD 2020v2 ranks workbook, a retired pin, on all 6,976 zones in all seven domains. The 189 existing history columns keep fingerprint ddb162ef89c7d52a and the 146 existing main columns 9515021d99099b43, both now pinned. Plan and review: docs/plans/Domain_Ranks_Plan.md.

Columns (41): simd2004_access_domain_rank, simd2004_education_domain_rank, simd2004_employment_domain_rank, simd2004_health_domain_rank, simd2004_housing_domain_rank, simd2004_income_domain_rank, simd2006_access_domain_rank, simd2006_crime_domain_rank, simd2006_education_domain_rank, simd2006_employment_domain_rank, simd2006_health_domain_rank, simd2006_housing_domain_rank, simd2006_income_domain_rank, simd2009v2_access_domain_rank, simd2009v2_crime_domain_rank, simd2009v2_education_domain_rank, simd2009v2_employment_domain_rank, simd2009v2_health_domain_rank, simd2009v2_housing_domain_rank, simd2009v2_income_domain_rank, simd2012_access_domain_rank, simd2012_crime_domain_rank, simd2012_education_domain_rank, simd2012_employment_domain_rank, simd2012_health_domain_rank, simd2012_housing_domain_rank, simd2012_income_domain_rank, simd2016_access_domain_rank, simd2016_crime_domain_rank, simd2016_education_domain_rank, simd2016_employment_domain_rank, simd2016_health_domain_rank, simd2016_housing_domain_rank, simd2016_income_domain_rank, simd2020v2_access_domain_rank, simd2020v2_crime_domain_rank, simd2020v2_education_domain_rank, simd2020v2_employment_domain_rank, simd2020v2_health_domain_rank, simd2020v2_housing_domain_rank, simd2020v2_income_domain_rank