Use correct average earnings parameter for the triple lock index (#1191)

* Fix statutory sick, maternity and paternity pay and SSMG

* Use correct average earnings forecast to determine triple lock index
Fixes #1184

* Fix Add student loan repayments to HBAI income #1181

Author: nikhilwoodruff

changelog_entry.yaml

@@ -0,0 +1,4 @@
+- bump: patch
+  changes:
+    fixed:
+    - Triple lock uses the average earnings index from the OBR.

policyengine_uk/parameters/gov/dwp/state_pension/triple_lock/active.yaml

@@ -2,4 +2,5 @@ description: The triple lock is active if this value is true.
 values:
   2010-01-01: true
 metadata:
-  label: Triple lock active
+  unit: bool
+  label: triple lock

policyengine_uk/parameters/gov/dwp/state_pension/triple_lock/create_triple_lock.py

@@ -8,7 +8,7 @@
 
 
 def add_triple_lock(parameters: ParameterNode) -> ParameterNode:
-    average_earnings = parameters.gov.obr.per_capita.employment_income
+    average_earnings = parameters.gov.obr.average_earnings
     cpi = parameters.gov.obr.consumer_price_index
     min_rate = parameters.gov.dwp.state_pension.triple_lock.minimum_rate
 

policyengine_uk/parameters/gov/dwp/state_pension/triple_lock/minimum_rate.yaml

@@ -3,4 +3,4 @@ values:
   2010-01-01: 0.025
 metadata:
   unit: /1
-  label: Triple lock minimum rate
+  label: triple lock minimum rate

policyengine_uk/parameters/gov/obr/average_earnings.yaml

@@ -0,0 +1,30 @@
+description: Average earnings index.
+values:
+  2008-01-01: 100.0
+  2009-01-01: 101.8
+  2010-01-01: 102.7
+  2011-01-01: 104.3
+  2012-01-01: 105.0
+  2013-01-01: 109.9
+  2014-01-01: 110.5
+  2015-01-01: 112.8
+  2016-01-01: 115.4
+  2017-01-01: 119.1
+  2018-01-01: 122.2
+  2019-01-01: 124.8
+  2020-01-01: 125.2
+  2021-01-01: 132.5
+  2022-01-01: 141.1
+  2023-01-01: 150.8
+  2024-01-01: 157.8
+  2025-01-01: 163.7
+  2026-01-01: 167.2
+  2027-01-01: 170.7
+  2028-01-01: 174.5
+  2029-01-01: 178.9
+metadata:
+  unit: currency-GBP
+  label: average earnings
+  reference:
+    - title: OBR EFO March 2025 (detailed forecast tables, economy, Table 1.6, Row Q)
+      href: https://obr.uk/efo/economic-and-fiscal-outlook-march-2025/

policyengine_uk/variables/gov/gov_tax.py

@@ -33,6 +33,7 @@ class gov_tax(Variable):
         "consumer_incident_tax_revenue_change",
         "high_income_incident_tax_change",
         "ni_employer",
+        "student_loan_repayments",
     ]
 
     def formula(household, period, parameters):

policyengine_uk/variables/gov/hmrc/household_tax.py

@@ -32,6 +32,7 @@ class household_tax(Variable):
         "high_income_incident_tax_change",
         "employer_ni_response_capital_incidence",
         "employer_ni_response_consumer_incidence",
+        "student_loan_repayments",
     ]
 
     def formula(household, period, parameters):

policyengine_uk/variables/gov/hmrc/student_loan_repayments.py

@@ -0,0 +1,10 @@
+from policyengine_uk.model_api import *
+
+
+class student_loan_repayments(Variable):
+    label = "student loan repayments"
+    entity = Person
+    definition_period = YEAR
+    value_type = float
+    unit = GBP
+    uprating = "gov.obr.average_earnings"

policyengine_uk/variables/household/income/hbai_household_net_income.py

@@ -62,6 +62,7 @@ class hbai_household_net_income(Variable):
         "wealth_tax",
         "income_tax",
         "national_insurance",
+        "student_loan_repayments",
     ]