sspl-allocation-is-part-of-the-contract

Date: 2026-09-12. Status: implemented.

Decision. The main table's data zones are the SSPL's: every higher geography is the one containing the centroid of the postcode's 2022 output area. The history table's data zones are the SPD's: the zone containing the postcode's own grid reference. Each table's metadata names its method (allocation: oa2022_centroid or postcode_grid_reference), the data dictionary states it, and every build reports how many current postcodes differ between the two tables and how many SIMD bands change as a result. The difference is an observation, never a gate, and never reconciled by editing either table.

Reason. A user must be able to see which allocation method a table follows. The comparison reports observed differences, not a causal decomposition into release and allocation effects. It compares own-record bands before linked-small-user selection. Neither shared inputs nor matching bands establish equivalence to a PHS postcode-level lookup.

Evidence. NRS information note and current build report. The preliminary SSPL 2026/1 comparison in the historical plan used different PAF cuts and incorrect representatives for 19 postcodes; its provisional counts and cause claims are not acceptance evidence.

Columns (50): CensusHouseholdCount1991, CensusHouseholdCount2001, CensusHouseholdCount2011, CensusHouseholdCount2022, CensusPopulationCount1991, CensusPopulationCount2001, CensusPopulationCount2011, CensusPopulationCount2022, CivilParish1930Code, CouncilArea2019Code, DataZone2001Code, DataZone2011Code, DataZone2022Code, DateOfDeletion, DateOfIntroduction, ElectoralWard2022Code, GridReferenceEasting, GridReferenceNorthing, HealthBoardArea1995Code, HealthBoardArea2006Code, HealthBoardArea2019Code, ITL2025Level2Code, ITL2025Level3Code, IntegrationAuthority2019Code, IntermediateZone2001Code, IntermediateZone2011Code, IntermediateZone2022Code, IslandCode, LAU2025Level1Code, LinkedSmallUserPostcode, LocalGovernmentDistrict1991Code, LocalGovernmentDistrict1995Code, OutputArea1991Code, OutputArea2001Code, OutputArea2011Code, OutputArea2022Code, Postcode, PostcodeDistrict, PostcodeSector, PostcodeType, RegistrationDistrict2007Code, ScottishIndexOfMultipleDeprivation2020Rank, ScottishParliamentaryConstituency2026Code, ScottishParliamentaryRegion2026Code, SplitIndicator, StrategicDevelopmentPlanningArea2013Code, TravelToWorkArea2011Code, UKParliamentaryConstituency2024Code, UrbanRural6Fold2022Code, UrbanRural8Fold2022Code