fix: correct Plan 2/5 values from EES permalink and add source breakdown

Author: nikhilwoodruff

policyengine_uk_data/targets/sources/slc.py

@@ -4,59 +4,79 @@
 borrowers liable to repay and earning above the repayment threshold.
 This matches the FRS coverage (PAYE deductions only).
 
-Source: SLC 'Student loans: borrower liability and repayment' statistical
-release, Table 6a — Forecast number of student borrowers liable to repay
-and number earning above repayment threshold.
-https://www.gov.uk/government/collections/student-loans-in-england-statistics
+Source: Explore Education Statistics — Student loan forecasts for England,
+Table 6a: Forecast number of student borrowers liable to repay and number
+earning above repayment threshold, by product. Figures are the sum of
+higher education full-time, higher education part-time, and advanced
+learner loan borrowers (Master's and Doctoral loans use Plan 3 and are
+excluded). Academic year 20XX-YY maps to calendar year 20XX.
+
+Data permalink:
+https://explore-education-statistics.service.gov.uk/data-tables/permalink/6ff75517-7124-487c-cb4e-08de6eccf22d
 """
 
 from policyengine_uk_data.targets.schema import Target, Unit
 
+_REFERENCE = (
+    "https://explore-education-statistics.service.gov.uk/data-tables"
+    "/permalink/6ff75517-7124-487c-cb4e-08de6eccf22d"
+)
+
+# Plan 2, earning above threshold — sum of HE full-time + part-time + AL
+# 2024-25: 3,670k + 225k + 90k = 3,985k
+# 2025-26: 4,130k + 245k + 85k = 4,460k
+# 2026-27: 4,480k + 260k + 85k = 4,825k
+# 2027-28: 4,700k + 265k + 80k = 5,045k
+# 2028-29: 4,820k + 265k + 70k = 5,155k
+# 2029-30: 4,870k + 270k + 65k = 5,205k
+_PLAN2_ABOVE_THRESHOLD = {
+    2025: 3_985_000,
+    2026: 4_460_000,
+    2027: 4_825_000,
+    2028: 5_045_000,
+    2029: 5_155_000,
+    2030: 5_205_000,
+}
+
+# Plan 5, earning above threshold — sum of HE full-time + part-time + AL
+# 2024-25: 0 + 0 + 0 = 0
+# 2025-26: 25k + 5k + 5k = 35k
+# 2026-27: 115k + 20k + 10k = 145k
+# 2027-28: 340k + 35k + 15k = 390k
+# 2028-29: 700k + 50k + 15k = 765k
+# 2029-30: 1,140k + 75k + 20k = 1,235k
+_PLAN5_ABOVE_THRESHOLD = {
+    2026: 35_000,
+    2027: 145_000,
+    2028: 390_000,
+    2029: 765_000,
+    2030: 1_235_000,
+}
+
 
 def get_targets() -> list[Target]:
     targets = []
 
-    _REFERENCE = (
-        "https://www.gov.uk/government/collections/"
-        "student-loans-in-england-statistics"
-    )
-
-    # Plan 2 — England, earning above threshold
-    # Academic year 20XX-YY maps to calendar year 20XX.
     targets.append(
         Target(
             name="slc/plan_2_borrowers_above_threshold",
             variable="student_loan_plan",
             source="slc",
             unit=Unit.COUNT,
             is_count=True,
-            values={
-                2025: 3_985_000,
-                2026: 4_460_000,
-                2027: 4_825_000,
-                2028: 5_045_000,
-                2029: 5_160_000,
-                2030: 5_205_000,
-            },
+            values=_PLAN2_ABOVE_THRESHOLD,
             reference_url=_REFERENCE,
         )
     )
 
-    # Plan 5 — England, earning above threshold
     targets.append(
         Target(
             name="slc/plan_5_borrowers_above_threshold",
             variable="student_loan_plan",
             source="slc",
             unit=Unit.COUNT,
             is_count=True,
-            values={
-                2026: 35_000,
-                2027: 145_000,
-                2028: 390_000,
-                2029: 770_000,
-                2030: 1_235_000,
-            },
+            values=_PLAN5_ABOVE_THRESHOLD,
             reference_url=_REFERENCE,
         )
     )

policyengine_uk_data/tests/test_student_loan_targets.py

@@ -20,7 +20,7 @@ def test_slc_plan2_values():
     p2 = targets["slc/plan_2_borrowers_above_threshold"]
     assert p2.values[2025] == 3_985_000
     assert p2.values[2026] == 4_460_000
-    assert p2.values[2029] == 5_160_000
+    assert p2.values[2029] == 5_155_000
 
 
 def test_slc_plan5_values():
@@ -31,4 +31,4 @@ def test_slc_plan5_values():
     p5 = targets["slc/plan_5_borrowers_above_threshold"]
     assert 2025 not in p5.values  # no Plan 5 borrowers yet in 2024-25
     assert p5.values[2026] == 35_000
-    assert p5.values[2029] == 770_000
+    assert p5.values[2029] == 765_000