Model take-up of itemized medical deduction

changelog_entry.yaml

@@ -0,0 +1,4 @@
+- bump: minor
+  changes:
+    added:
+    - Itemized medical deduction take-up.

policyengine_us/parameters/gov/irs/deductions/itemized/medical/takeup.yaml

@@ -0,0 +1,10 @@
+description: The share of eligible taxpayers who claim the itemized medical deduction.
+values:
+  20224-01-01: 0.505
+metadata:
+  period: year
+  unit: /1
+  label: Itemized medical deduction takeup rate
+  reference:
+    - title: Subsidizing Medical Spending Through the Tax Code: Take-Up, Targeting and the Cost of Claiming
+      href: https://www.nber.org/system/files/working_papers/w33213/w33213.pdf#page=2

policyengine_us/variables/gov/irs/income/taxable_income/deductions/itemizing/medical_expense_deduction.py

@@ -11,7 +11,13 @@ class medical_expense_deduction(Variable):
     documentation = "Medical expenses deducted from taxable income."
 
     def formula(tax_unit, period, parameters):
+        takes_up_itemized_medical_deduction = tax_unit(
+            "takes_up_itemized_medical_deduction", period
+        )
         expense = add(tax_unit, period, ["medical_out_of_pocket_expenses"])
         medical = parameters(period).gov.irs.deductions.itemized.medical
         medical_floor = medical.floor * tax_unit("positive_agi", period)
-        return max_(0, expense - medical_floor)
+        return (
+            max_(0, expense - medical_floor)
+            * takes_up_itemized_medical_deduction
+        )

policyengine_us/variables/gov/irs/income/taxable_income/deductions/itemizing/takes_up_itemized_medical_deduction.py

@@ -0,0 +1,14 @@
+from policyengine_us.model_api import *
+
+
+class takes_up_itemized_medical_deduction(Variable):
+    value_type = bool
+    entity = TaxUnit
+    label = "Takes up the itemized medical deduction"
+    definition_period = YEAR
+
+    def formula(tax_unit, period, parameters):
+        if not hasattr(tax_unit.simulation, "dataset"):
+            return True
+        takeup_rate = parameters(period).gov.irs.deductions.medical.takeup
+        return random(tax_unit) < takeup_rate