Tighten disability category thresholds

policyengine_uk_data/datasets/disability_benefits.py

@@ -47,7 +47,7 @@
     "esa_income_reported",
 )
 
-SAFETY_MARGIN = 0.1
+CATEGORY_THRESHOLD_WEEKLY_TOLERANCE = 1.0
 SURVEY_REPORTED_AMOUNT_WEEKS_IN_YEAR = 365.25 / 7
 
 
@@ -88,9 +88,14 @@ def _category_from_reported_amount(
     weekly_amount = weekly_amount.to_numpy(dtype=float) / MODEL_WEEKS_IN_YEAR
     category = np.full(len(weekly_amount), "NONE", dtype=object)
     for category_name, weekly_rate in thresholds:
-        category[weekly_amount >= float(weekly_rate) * (1 - SAFETY_MARGIN)] = (
-            category_name
+        # FRS benefit amounts are weekly survey responses annualised upstream;
+        # allow GBP 1/week of rounding noise without discounting rates by a
+        # percentage that can promote people into higher award categories.
+        threshold = max(
+            0.0,
+            float(weekly_rate) - CATEGORY_THRESHOLD_WEEKLY_TOLERANCE,
         )
+        category[weekly_amount >= threshold] = category_name
     return category
 
 

policyengine_uk_data/tests/test_disability_benefits.py

@@ -16,32 +16,36 @@
 def test_reported_amounts_map_to_disability_categories():
     year = 2025
     dwp = CountryTaxBenefitSystem().parameters(year).baseline.gov.dwp
+
+    def annual_near_threshold(weekly_rate):
+        return (weekly_rate - 0.5) * WEEKS_IN_YEAR
+
     person = pd.DataFrame(
         {
             "attendance_allowance_reported": [
                 0,
-                dwp.attendance_allowance.lower * WEEKS_IN_YEAR * 0.91,
-                dwp.attendance_allowance.higher * WEEKS_IN_YEAR * 0.91,
+                annual_near_threshold(dwp.attendance_allowance.lower),
+                annual_near_threshold(dwp.attendance_allowance.higher),
             ],
             "dla_sc_reported": [
                 0,
-                dwp.dla.self_care.lower * WEEKS_IN_YEAR * 0.91,
-                dwp.dla.self_care.middle * WEEKS_IN_YEAR * 0.91,
+                annual_near_threshold(dwp.dla.self_care.lower),
+                annual_near_threshold(dwp.dla.self_care.middle),
             ],
             "dla_m_reported": [
                 0,
-                dwp.dla.mobility.lower * WEEKS_IN_YEAR * 0.91,
-                dwp.dla.mobility.higher * WEEKS_IN_YEAR * 0.91,
+                annual_near_threshold(dwp.dla.mobility.lower),
+                annual_near_threshold(dwp.dla.mobility.higher),
             ],
             "pip_m_reported": [
                 0,
-                dwp.pip.mobility.standard * WEEKS_IN_YEAR * 0.91,
-                dwp.pip.mobility.enhanced * WEEKS_IN_YEAR * 0.91,
+                annual_near_threshold(dwp.pip.mobility.standard),
+                annual_near_threshold(dwp.pip.mobility.enhanced),
             ],
             "pip_dl_reported": [
                 0,
-                dwp.pip.daily_living.standard * WEEKS_IN_YEAR * 0.91,
-                dwp.pip.daily_living.enhanced * WEEKS_IN_YEAR * 0.91,
+                annual_near_threshold(dwp.pip.daily_living.standard),
+                annual_near_threshold(dwp.pip.daily_living.enhanced),
             ],
         }
     )
@@ -55,6 +59,30 @@ def test_reported_amounts_map_to_disability_categories():
     assert result["pip_dl_category"].tolist() == ["NONE", "STANDARD", "ENHANCED"]
 
 
+def test_reported_amounts_do_not_use_percentage_category_margin():
+    year = 2025
+    dwp = CountryTaxBenefitSystem().parameters(year).baseline.gov.dwp
+    person = pd.DataFrame(
+        {
+            "attendance_allowance_reported": [
+                dwp.attendance_allowance.higher * WEEKS_IN_YEAR * 0.91,
+            ],
+            "pip_dl_reported": [
+                dwp.pip.daily_living.standard * WEEKS_IN_YEAR * 0.91,
+            ],
+            "pip_m_reported": [
+                dwp.pip.mobility.enhanced * WEEKS_IN_YEAR * 0.91,
+            ],
+        }
+    )
+
+    result = add_disability_benefit_categories_from_reported_amounts(person, year)
+
+    assert result["aa_category"].tolist() == ["LOWER"]
+    assert result["pip_dl_category"].tolist() == ["NONE"]
+    assert result["pip_m_category"].tolist() == ["STANDARD"]
+
+
 def test_reported_amounts_recompute_disability_flags():
     year = 2025
     dwp = CountryTaxBenefitSystem().parameters(year).gov.dwp