UK source packages: UC payment-status × child-entitlement composition crosses

[juaristi22]

Chronicle already exports the UC pairwise breakdowns added by #239, which closed #233 and #234. The remaining source gap is the joint distribution of payment status and child entitlement by family type / number of children.

At main f31d902, the archived publisher responses contain:

• Month × Family Type × Payment Indicator.
• Month × Family Type × Child Entitlement.
• Month × Number of Children × Child Entitlement.

These margins do not identify the joint. DWP's Payment Indicator distinguishes payment from a nil award among households with a calculated award; Child Entitlement records child-element entitlement. Neither substitutes for the other.

Requested source exports

Verify that Stat-Xplore permits the following UC_Households count queries, then package the unchanged publisher results:

1. Month × Family Type × Payment Indicator × Child Entitlement.
2. Month × Number of Children × Payment Indicator × Child Entitlement.
3. A direct publisher Payment Indicator × Number of Children margin for each month, if query 2 cannot include an independently published Total over Child Entitlement. Do not emit a sum of the joint cells as an observed marginal fact.

Use the existing Great Britain, April–December 2025 observation window. The archived queries above supply the dataset, count measure, month recodes and field IDs: hnfamily_type, NUMBER_OF_CHILDREN, HCPAYMENT and HCCHILD_ENTITLEMENT. The DWP table API supports multiple fields within an axis. Combining the archived query fields gives a reproducible starting point, but the new combined queries still need an actual publisher response; if a combination is unavailable or restricted, record that limitation explicitly instead of inferring its cells.

Preserve both Yes/No categories, all publisher-emitted family/child-count categories, unknown/not-available codes, and any suppressed/missing values with their annotations. Do not convert them to zero or pool them silently. DWP's Number of Children definition counts verified declared under-20s and cannot reliably identify whether each child is a dependant or a child of the claimant. Adding Child Entitlement must not rename that axis as qualifying children or children receiving an element.

Acceptance criteria

• Archive the exact request and response, including field/value IDs, labels, month list, revision and disclosure annotations; pin source URL, extraction date, vintage, byte size, SHA-256 and raw-storage pointer.
• Emit publisher counts as benefit-unit observations, GB K03000001, period.type: month, with explicit payment, child-entitlement and composition dimensions. Preserve source-row/source-cell lineage and distinguish any publisher Total from detail measures.
• Check exact requested-versus-returned month and category coverage. Preserve any unavailable/suppressed combinations explicitly; do not fabricate zero observations or infer a joint from pairwise margins.
• Where contemporaneous publisher margins are returned, test reconciliation with the publisher's disclosure-control tolerance. Do not force equality by rewriting source values, especially across release vintages.
• Add package validation, source-preservation and consumer-bundle tests; retain existing vocabulary and document any unavoidable identity migration.

Scope and existing ownership

#247 / open PR #250 already covers the published family-type Total and April–December histories for 2023–2025. This issue does not duplicate that work or request January–March / full-calendar extensions without establishing source availability.

Chronicle owns the publisher facts and their provenance. Microcosm owns target selection, any averaging or annualisation, model-child/claim-state mappings and calibration; those consumer concerns remain in Microcosm #882. This issue neither changes a calibration target nor claims that the additional crosses resolve the UC model discrepancy.

[juaristi22]

Window update (María's direction, 2026-09-08): the two crosses are ported for April 2023 through the most recent published month (May 2026, the last month in DWP's 18 August 2026 quarterly release), not only April–December 2025. Stat-Xplore rejects June 2026 as an invalid month value, which fixes the end of the window. Query 2 returned the publisher Total over Child Entitlement directly (total: true on the recode), so the fallback margin query in item 3 was not needed. PR: #252 (draft, rebased over #250).