Port UK compact source stages and 2024-25 refresh from uk-data

Parent: PolicyEngine/populace#144.

Why

Populace UK can replace the local-geography/matrix path, and the current compact H5 already carries several recent uk-data columns. But if policyengine-uk-data is archived, Populace needs to own the source-stage logic and provenance for those columns instead of relying on uk-data build history.

Scope migrated from uk-data

Open PRs:

• PolicyEngine/policyengine-uk-data#426: mortgage_debt and consumer_debt from WAS for net_wealth.
• PolicyEngine/policyengine-uk-data#408: pip_dl_points / pip_m_points from PIP categories once model variables exist.

Recent merged PRs that need Populace-owned source-stage equivalents:

• #410/#436: FRS 2024-25 ingestion plus household-ID sort invariant for raw compact builds.
• #433: employment_sector, sic_industry_division, and public-sector target source.
• #428/#429/#431: bus_fare_spending, bus subsidy scaling, and model-version floor.
• #425: seeded stochastic draws for property purchase, BRMA, and capital-gains amounts.
• #421: SPI synthetic prior weights, household_is_spi_synthetic, household_is_capital_gains_clone, and calibration source-share diagnostics.
• #380/#383/#416/#417/#419: disability, PIP category, child/QYP, and transfer-side PIP component fixes.
• #372/#385/#403-#407/#412-#414: income/SPI/fuel/consumption prerequisite updates and road-fuel volume uprating.

Acceptance criteria

• Populace has UK source-stage modules/manifests for these compact-data inputs, with no policyengine_uk_data imports.
• The compact artifact can be rebuilt for at least the current Populace UK release year and the FRS 2024-25 refresh path.
• Export-variable gates prove the compact H5 includes the same PolicyEngine-UK variables expected by policyengine.py.
• Determinism tests cover every stochastic assignment on the live build path.
• Source flags and diagnostics make synthetic SPI/capital-gains support inspectable without row-order inference.

2026-08-12 update — this issue is workstream E of the UK-migration master epic #665 (it absorbs the source-stage track of the now-closed #144).

Full item list to port, each as a declarative source stage + gate (children filed as picked up); order constraints: wealth before consumption (num_vehicles), income before capital gains.

• Full FRS table ingest (incumbent reads ~14 tables; microcosm reads 2): entities/IDs, grossing weights, demographics, council-tax imputation, LHA/BRMA, education, legacy-benefit proxies, disability categories
• Stochastic inputs: 11 take-up parameter files with reported-receipt anchoring, TV licence/FTB draws, seeded RNG discipline, household_is_* provenance flags as first-class metadata
• WAS wealth (11 outputs incl. num_vehicles, student-loan balance allocation) — note the owned_land release-to-release instability recorded in PolicyEngine/policyengine-uk-data#448
• LCFS consumption (18 outputs) + energy raking to NEED targets
• ETB VAT; ETB services + NHS usage
• Capital gains incl. top tail (#560 in flight; #552/#364/#467)
• Salary sacrifice; student loan plans (SLC stocks); childcare take-up fitting; regional property uprating
• From #144: debt, bus fares (#153), employer sector/SIC, PIP/disability, child/QYP
• New stages requested against the incumbent that land here instead: UC deduction attributes (PolicyEngine/policyengine-uk-data#450)
• Known incumbent defects the ports must not replicate: UC caseload ~40% below administrative counts (PolicyEngine/policyengine-uk-data#452), Scottish/Welsh council tax 20–30% above devolved budgets (PolicyEngine/policyengine-uk-data#448)
• FRS 2024-25 refresh (incumbent is already there; calibration year 2025)

Acceptance: the microcosm-built spine replaces the certified incumbent H5 in the national build; eFRS parity fixtures beat or match the incumbent on the frozen register with signed differences.

Start by mapping the source-stage modules and manifests required for the compact H5 build, then inspect policyengine.py for the expected export variables. Trace the current Populace build and FRS 2024-25 refresh path, including stochastic assignments and provenance diagnostics. Done means the microcosm-built spine replaces the incumbent H5 with export gates, determinism tests, inspectable source flags, and eFRS parity fixtures.