Merge pull request #1338 from PolicyEngine/add-real-ahc

Add real_hbai_household_net_income_ahc variable for convenience

Author: janton10

changelog_entry.yaml

@@ -0,0 +1,4 @@
+- bump: minor
+  changes:
+    fixed:
+      - Add real_hbai_household_net_income_ahc variable for convenience.

policyengine_uk/variables/household/income/hbai_household_net_income_ahc.py

@@ -17,3 +17,16 @@ class hbai_household_net_income_ahc(Variable):
         "mortgage_interest_repayment",
         "structural_insurance_payments",
     ]
+
+
+class real_hbai_household_net_income_ahc(Variable):
+    label = "real household net income after housing costs (HBAI definition)"
+    entity = Household
+    definition_period = YEAR
+    value_type = float
+    unit = GBP
+
+    def formula(household, period, parameters):
+        return household("hbai_household_net_income_ahc", period) * household(
+            "inflation_adjustment_ahc", period
+        )

policyengine_uk/variables/household/income/inflation_adjustment.py

@@ -19,3 +19,27 @@ def formula(household, period, parameters):
         current_period_cpi = cpi(period)
         now_cpi = cpi(datetime.datetime.now().strftime("%Y-01-01"))
         return now_cpi / current_period_cpi
+
+
+class inflation_adjustment_ahc(Variable):
+    label = f"inflation multiplier to get {datetime.datetime.now().year} after housing costs prices"
+    entity = Household
+    definition_period = YEAR
+    value_type = float
+    unit = "/1"
+
+    def formula(household, period, parameters):
+        cpi = (
+            parameters.gov.economic_assumptions.indices.obr.consumer_price_index
+        )
+        cpi_ahc = (
+            parameters.gov.economic_assumptions.indices.obr.consumer_price_index_ahc
+        )
+
+        cpi_ahc_val = cpi_ahc(period)
+        # Fall back to use cpi, for periods beyond 2029
+        if not cpi_ahc_val:
+            cpi_ahc_val = cpi(period)
+
+        now_cpi_ahc = cpi(datetime.datetime.now().strftime("%Y-01-01"))
+        return now_cpi_ahc / cpi_ahc_val