No calibration targets for UC elements: childcare runs 2.3x official, housing/LCWRA/carer unbenchmarked

[vahid-ahmadi]

Most of UC entitlement is calibrated against nothing. sources/dwp.py targets caseload, family type, payment bands, deductions and the two-child limit — but no element counts. Only the childcare element has a published comparator, and the model is 2.3x it.

Model vs official, enhanced FRS 2023-24 v1.56.16, 2025:

Element	Model recipients	Official	Err
Childcare	370k	160k	+131%
Child	3.077m (48.1% of hh)	47% of hh	ok
Housing	5.193m	—	no target
LCWRA / health	2.041m	—	no target
Carer	0.560m	—	no target

Childcare official: UC statistics to 9 Oct 2025 (160k Aug 2025, 170k Aug 2024). The rest are Stat-Xplore UC_Households only — not in any bulletin.

Related: family-type targets sum to 6.096m against a dwp/uc/households target of 6.7m (the vintage tension noted in #458), and the 3+ children rows run 16-22% low:

Family type	Model	DWP	Err
Single, no children	3.210m	2.868m	+11.9%
Couple, no children	0.280m	0.231m	+21.1%
3 children	0.369m	0.473m	-22.0%
4 children	0.136m	0.167m	-18.3%
5+ children	0.064m	0.076m	-16.2%

Next steps

1. Register a Stat-Xplore API key and add element-count targets for housing, LCWRA, carer, childcare from UC_Households.
2. Add the childcare 160k target now — it is published and needs no key.
3. Refresh the family-type values to a current Stat-Xplore month so they sum consistently with dwp/uc/households (the Fix Universal Credit caseload targets #458 follow-up).
4. Once these exist, microcosm#729's national_calibration.py picks them up through the reference registry; no microcosm change needed until then.

cc @MaxGhenis @vahid-ahmadi

[vahid-ahmadi]

Correction to my earlier note: the dependency runs the other way and starts upstream of here. Per PolicyEngine/microcosm#738, no contract ids exist for the elements because no facts exist — the pipeline is chronicle facts first (PolicyEngine/chronicle#187: childcare's published 160k needs no key; housing/LCWRA/carer need Stat-Xplore UC_Households), then the targets here, then microcosm references activate automatically. Tracked as microcosm#736 item 12.