Source local LA uprating factors from policyengine-uk

changelog.d/local-la-uprating-from-policyengine-uk.changed.md

@@ -0,0 +1 @@
+Read local-authority ONS income uprating assumptions from `policyengine-uk` parameters when available, while keeping a compatibility fallback for the current released dependency.

policyengine_uk_data/datasets/local_areas/local_authorities/loss.py

@@ -32,12 +32,11 @@
     get_la_uc_targets,
 )
 from policyengine_uk_data.targets.sources.local_la_extras import (
+    get_ons_income_uprating_factors,
     load_ons_la_income,
     load_household_counts,
     load_tenure_data,
     load_private_rents,
-    UPRATING_NET_INCOME_BHC_2020_TO_2025,
-    UPRATING_HOUSING_COSTS_2020_TO_2025,
 )
 
 
@@ -127,6 +126,9 @@ def create_local_authority_target_matrix(
     hbai_net_income = sim.calculate("equiv_hbai_household_net_income").values
     hbai_net_income_ahc = sim.calculate("equiv_hbai_household_net_income_ahc").values
     housing_costs = hbai_net_income - hbai_net_income_ahc
+    income_bhc_uprating_factor, housing_costs_uprating_factor = (
+        get_ons_income_uprating_factors(int(time_period))
+    )
 
     matrix["ons/equiv_net_income_bhc"] = hbai_net_income
     matrix["ons/equiv_net_income_ahc"] = hbai_net_income_ahc
@@ -135,12 +137,12 @@ def create_local_authority_target_matrix(
     ons_merged["equiv_net_income_bhc_target"] = (
         ons_merged["net_income_bhc"]
         * ons_merged["households"]
-        * UPRATING_NET_INCOME_BHC_2020_TO_2025
+        * income_bhc_uprating_factor
     )
     ons_merged["equiv_housing_costs_target"] = (
         ons_merged["net_income_bhc"] * ons_merged["households"]
         - ons_merged["net_income_ahc"] * ons_merged["households"]
-    ) * UPRATING_HOUSING_COSTS_2020_TO_2025
+    ) * housing_costs_uprating_factor
     ons_merged["equiv_net_income_ahc_target"] = (
         ons_merged["equiv_net_income_bhc_target"]
         - ons_merged["equiv_housing_costs_target"]

policyengine_uk_data/targets/sources/local_la_extras.py

@@ -14,14 +14,19 @@
 import logging
 
 import pandas as pd
+from policyengine_uk.system import system
 
 from policyengine_uk_data.targets.sources._common import STORAGE
 
 logger = logging.getLogger(__name__)
 
-# Uprating factors from FYE 2020 to 2025 (OBR Nov 2025 EFO)
-UPRATING_NET_INCOME_BHC_2020_TO_2025 = 1985.1 / 1467.6
-UPRATING_HOUSING_COSTS_2020_TO_2025 = 103.5 / 84.9
+# Compatibility fallback until policyengine-uk ships the matching parameters.
+_LEGACY_ONS_INCOME_UPRATING_FACTORS = {
+    2025: (
+        1985.1 / 1467.6,
+        103.5 / 84.9,
+    ),
+}
 
 _REF_ONS_INCOME = (
     "https://www.ons.gov.uk/employmentandlabourmarket/peopleinwork/"
@@ -35,6 +40,31 @@
 )
 
 
+def get_ons_income_uprating_factors(year: int) -> tuple[float, float]:
+    """Return BHC-income and housing-cost uprating factors for LA ONS targets."""
+    econ_assumptions = system.parameters.gov.economic_assumptions
+    local_authority_targets = getattr(econ_assumptions, "local_authority_targets", None)
+
+    if local_authority_targets is not None:
+        ons_income = local_authority_targets.ons_income
+        net_income_bhc = ons_income.net_income_bhc_uprating_factor(f"{year}-01-01")
+        housing_costs = ons_income.housing_costs_uprating_factor(f"{year}-01-01")
+        if net_income_bhc is None or housing_costs is None:
+            raise ValueError(
+                f"policyengine-uk local authority target uprating factors are "
+                f"incomplete for {year}."
+            )
+        return float(net_income_bhc), float(housing_costs)
+
+    if year in _LEGACY_ONS_INCOME_UPRATING_FACTORS:
+        return _LEGACY_ONS_INCOME_UPRATING_FACTORS[year]
+
+    raise ValueError(
+        f"No ONS LA income uprating factors configured for {year}. "
+        "Update policyengine-uk or add a compatibility fallback."
+    )
+
+
 def load_ons_la_income() -> pd.DataFrame:
     """Load ONS income estimates by local authority.
 

policyengine_uk_data/tests/test_local_la_extras.py

@@ -0,0 +1,71 @@
+from types import SimpleNamespace
+
+import pytest
+
+from policyengine_uk_data.targets.sources import local_la_extras
+
+
+def test_get_ons_income_uprating_factors_uses_legacy_2025_fallback():
+    assert local_la_extras.get_ons_income_uprating_factors(2025) == (
+        1985.1 / 1467.6,
+        103.5 / 84.9,
+    )
+
+
+def test_get_ons_income_uprating_factors_prefers_policyengine_uk_parameters(
+    monkeypatch,
+):
+    params = SimpleNamespace(
+        gov=SimpleNamespace(
+            economic_assumptions=SimpleNamespace(
+                local_authority_targets=SimpleNamespace(
+                    ons_income=SimpleNamespace(
+                        net_income_bhc_uprating_factor=lambda _: 1.5,
+                        housing_costs_uprating_factor=lambda _: 1.25,
+                    )
+                )
+            )
+        )
+    )
+
+    monkeypatch.setattr(
+        local_la_extras,
+        "system",
+        SimpleNamespace(parameters=params),
+    )
+
+    assert local_la_extras.get_ons_income_uprating_factors(2025) == (1.5, 1.25)
+
+
+def test_get_ons_income_uprating_factors_raises_for_unknown_year(monkeypatch):
+    params = SimpleNamespace(
+        gov=SimpleNamespace(economic_assumptions=SimpleNamespace())
+    )
+    monkeypatch.setattr(
+        local_la_extras,
+        "system",
+        SimpleNamespace(parameters=params),
+    )
+
+    with pytest.raises(ValueError, match="No ONS LA income uprating factors"):
+        local_la_extras.get_ons_income_uprating_factors(2024)
+
+
+def test_get_ons_income_uprating_factors_raises_for_partial_upstream_tree(
+    monkeypatch,
+):
+    params = SimpleNamespace(
+        gov=SimpleNamespace(
+            economic_assumptions=SimpleNamespace(
+                local_authority_targets=SimpleNamespace()
+            )
+        )
+    )
+    monkeypatch.setattr(
+        local_la_extras,
+        "system",
+        SimpleNamespace(parameters=params),
+    )
+
+    with pytest.raises(AttributeError):
+        local_la_extras.get_ons_income_uprating_factors(2025)