Correct the 2020 over-75 TV licence transition

changelog.d/2151.fixed.md

@@ -0,0 +1 @@
+- Corrected the 2020 over-75 TV licence Pension Credit transition to start on 1 August while preserving its Boolean eligibility rule.

policyengine_uk/parameters/gov/dcms/bbc/tv_licence/discount/aged/discount.yaml

@@ -2,8 +2,9 @@ description: Percentage discount for qualifying aged households.
 values:
   2003-01-01: 1
 metadata:
+  preserve_calendar_dates: true
   unit: /1
   label: Aged TV Licence discount
   reference:
     - title: "Free and reduced fee TV Licences | TV Licensing"
-      href: https://www.tvlicensing.co.uk/reducedfee
+      href: https://www.tvlicensing.co.uk/reducedfee

policyengine_uk/parameters/gov/dcms/bbc/tv_licence/discount/aged/min_age.yaml

@@ -2,6 +2,7 @@ description: Minimum age required to qualify for a TV licence discount.
 values:
   2003-01-01: 75
 metadata:
+  preserve_calendar_dates: true
   unit: year
   label: Aged TV Licence discounted minimum age
   reference:

policyengine_uk/parameters/gov/dcms/bbc/tv_licence/discount/aged/must_claim_pc.yaml

@@ -1,10 +1,16 @@
-description: Whether aged individuals must claim Pension Credit in order to qualify for a free TV licence.
+description: Whether aged individuals must receive Pension Credit to qualify for a free TV licence.
 values:
   2003-01-01: false
-  2020-04-01: true
+  2020-08-01:
+    value: true
+    reference:
+      - title: Government and BBC joint statement on delaying the TV licence fee for over 75s
+        href: https://www.gov.uk/government/news/bbc-and-governments-joint-statement-on-delaying-the-tv-licence-fee-for-over-75s
 metadata:
+  preserve_calendar_dates: true
   unit: bool
+  period: year
   label: Aged TV Licence Pension Credit requirement
   reference:
-    - title: "Free and reduced fee TV Licences | TV Licensing"
-      href: https://www.tvlicensing.co.uk/reducedfee
+    - title: Get a free or discounted TV licence
+      href: https://www.gov.uk/free-discount-tv-licence

policyengine_uk/tests/policy/baseline/gov/dcms/bbc/tv_licence_discount.yaml

@@ -41,4 +41,41 @@
     pension_credit: 1
     is_blind: true
   output:
-    tv_licence_discount: 1
+    tv_licence_discount: 1
+
+- name: All aged households qualify before the Pension Credit condition.
+  period: 2019
+  input:
+    age: 75
+    pension_credit: 0
+    is_blind: false
+  output:
+    tv_licence_discount: 1
+
+- name: The 2020-21 discount reflects the 1 August transition.
+  period: 2020
+  absolute_error_margin: 0.000001
+  input:
+    age: 75
+    pension_credit: 0
+    is_blind: false
+  output:
+    tv_licence_discount: 0.3205479452
+
+- name: Pension Credit recipients retain the full 2020-21 discount.
+  period: 2020
+  input:
+    age: 75
+    pension_credit: 1
+    is_blind: false
+  output:
+    tv_licence_discount: 1
+
+- name: The Pension Credit condition applies for all of 2021-22.
+  period: 2021
+  input:
+    age: 75
+    pension_credit: 0
+    is_blind: false
+  output:
+    tv_licence_discount: 0

policyengine_uk/tests/test_tv_licence_transition.py

@@ -0,0 +1,81 @@
+"""Tests for the 2020 over-75 TV licence concession transition."""
+
+from pathlib import Path
+
+import pytest
+from policyengine_core.parameters import ParameterNode
+
+import policyengine_uk
+from policyengine_uk import CountryTaxBenefitSystem, Simulation
+from policyengine_uk.utils.excise import fiscal_year_segments
+
+
+def _requirement(parameter_root):
+    return parameter_root.gov.dcms.bbc.tv_licence.discount.aged.must_claim_pc
+
+
+def test_pension_credit_condition_uses_the_statutory_start_date():
+    """The BBC deferred the condition from 1 June to 1 August 2020."""
+    parameters = ParameterNode(
+        directory_path=str(Path(policyengine_uk.__file__).parent / "parameters")
+    )
+    requirement = _requirement(parameters)
+
+    assert requirement("2020-07-31") is False
+    assert requirement("2020-08-01") is True
+
+
+def test_pension_credit_condition_keeps_its_date_after_processing():
+    """Processing preserves the 1 August Boolean policy transition."""
+    system = CountryTaxBenefitSystem()
+    requirement = _requirement(system.parameters)
+
+    assert requirement("2020-07-31") is False
+    assert requirement("2020-08-01") is True
+
+
+def test_pension_credit_condition_segments_the_2020_21_fiscal_year():
+    """The fiscal year has 117 unrestricted and 248 restricted days."""
+    system = CountryTaxBenefitSystem()
+    aged_rules = system.parameters.gov.dcms.bbc.tv_licence.discount.aged
+    segments = list(fiscal_year_segments(aged_rules, 2020))
+
+    unrestricted_share = sum(
+        share for rules, share in segments if not rules.must_claim_pc
+    )
+    restricted_share = sum(share for rules, share in segments if rules.must_claim_pc)
+
+    assert unrestricted_share == pytest.approx(117 / 365)
+    assert restricted_share == pytest.approx(248 / 365)
+    assert all(isinstance(rules.must_claim_pc, bool) for rules, _ in segments)
+
+
+def test_year_keyed_minimum_age_reform_applies_to_one_fiscal_year():
+    """A bare-year age reform must not be split across adjacent years."""
+    years = (2024, 2025, 2026)
+    situation = {
+        "people": {
+            "person": {
+                "age": {str(year): 72 for year in years},
+            },
+        },
+        "benunits": {
+            "benunit": {
+                "members": ["person"],
+                "pension_credit": {str(year): 1 for year in years},
+            },
+        },
+        "households": {
+            "household": {
+                "members": ["person"],
+            },
+        },
+    }
+    reform = {
+        "gov.dcms.bbc.tv_licence.discount.aged.min_age": {"2025": 70},
+    }
+    simulation = Simulation(situation=situation, reform=reform)
+
+    discounts = [simulation.calculate("tv_licence_discount", year)[0] for year in years]
+
+    assert discounts == pytest.approx([0, 1, 0])

policyengine_uk/variables/gov/dcms/bbc/tv_licence/tv_licence_discount.py

@@ -1,4 +1,5 @@
 from policyengine_uk.model_api import *
+from policyengine_uk.utils.excise import fiscal_year_segments
 
 
 class tv_licence_discount(Variable):
@@ -9,20 +10,27 @@ class tv_licence_discount(Variable):
     unit = "/1"
     reference = (
         "https://www.legislation.gov.uk/ukpga/2003/21/section/365A",
-        "https://www.tvlicensing.co.uk/reducedfee",
+        "https://www.gov.uk/government/news/bbc-and-governments-joint-statement-on-delaying-the-tv-licence-fee-for-over-75s",
+        "https://www.gov.uk/free-discount-tv-licence",
     )
 
     def formula(household, period, parameters):
         person = household.members
         tv_licence = parameters(period).gov.dcms.bbc.tv_licence
 
         # Aged discount
-        aged = person("age", period) >= tv_licence.discount.aged.min_age
-        has_aged = household.any(aged)
         claims_pc = add(household, period, ["pension_credit"]) > 0
-        meets_pc_requirement = not_(tv_licence.discount.aged.must_claim_pc) | claims_pc
-        eligible_for_aged_discount = has_aged & meets_pc_requirement
-        aged_discount = eligible_for_aged_discount * tv_licence.discount.aged.discount
+        aged_discount = 0
+        for aged_rules, share in fiscal_year_segments(
+            parameters.gov.dcms.bbc.tv_licence.discount.aged,
+            period.start.year,
+        ):
+            aged = person("age", period) >= aged_rules.min_age
+            has_aged = household.any(aged)
+            meets_pc_requirement = not_(aged_rules.must_claim_pc) | claims_pc
+            aged_discount += (
+                has_aged * meets_pc_requirement * aged_rules.discount * share
+            )
 
         # Blind discount
         is_blind = person("is_blind", period)