Model Medicare Part B premiums net of MSP coverage

changelog.d/codex-medicare-partb-msp-clean.fixed.md

@@ -0,0 +1 @@
+Model Medicare Part B premiums in baseline SPM expenses, preserve reported premiums as an audit input, and net out a cycle-free MSP proxy so baseline MOOP better reflects likely beneficiary out-of-pocket premiums.

policyengine_us/parameters/gov/irs/gross_income/pre_tax_contributions.yaml

@@ -4,8 +4,9 @@ values:
     # Assumes all are pre-tax.
     - traditional_401k_contributions
     - traditional_403b_contributions
-    # Assumes employer for now.
-    - health_insurance_premiums
+    # Assumes employer-sponsored premiums only; Medicare Part B is not a
+    # pre-tax payroll deduction.
+    - health_insurance_premiums_without_medicare_part_b
     # HSA contributions can be either through pre-tax.
     - health_savings_account_payroll_contributions
 metadata:

policyengine_us/tests/policy/baseline/gov/hhs/medicare/savings_programs/msp_part_b_premium_coverage.yaml

@@ -0,0 +1,29 @@
+- name: MSP part B coverage pays the standard premium for income- and asset-eligible enrollees
+  period: 2025
+  input:
+    medicare_enrolled: true
+    msp_income_eligible: true
+    msp_asset_eligible: true
+    base_part_b_premium: 2_220
+  output:
+    msp_part_b_premium_coverage: 2_220
+
+- name: MSP part B coverage is zero for ineligible enrollees
+  period: 2025
+  input:
+    medicare_enrolled: true
+    msp_income_eligible: false
+    msp_asset_eligible: true
+    base_part_b_premium: 2_220
+  output:
+    msp_part_b_premium_coverage: 0
+
+- name: MSP part B coverage is zero when not enrolled
+  period: 2025
+  input:
+    medicare_enrolled: false
+    msp_income_eligible: true
+    msp_asset_eligible: true
+    base_part_b_premium: 2_220
+  output:
+    msp_part_b_premium_coverage: 0

policyengine_us/tests/policy/baseline/gov/hhs/medicare/test_part_b_msp_offset.py

@@ -0,0 +1,260 @@
+import pytest
+
+from policyengine_us import CountryTaxBenefitSystem, Simulation
+
+
+SYSTEM = CountryTaxBenefitSystem()
+PERIOD = "2025"
+
+
+def make_simulation(
+    *,
+    medicare_enrolled: bool,
+    gross_part_b_premium: float,
+    base_part_b_premium: float,
+    msp_income_eligible: bool,
+    msp_asset_eligible: bool,
+) -> Simulation:
+    return Simulation(
+        tax_benefit_system=SYSTEM,
+        situation={
+            "people": {
+                "person": {
+                    "age": {PERIOD: 65},
+                    "medicare_enrolled": {PERIOD: medicare_enrolled},
+                    "income_adjusted_part_b_premium": {PERIOD: gross_part_b_premium},
+                    "base_part_b_premium": {PERIOD: base_part_b_premium},
+                    "msp_income_eligible": {f"{PERIOD}-01": msp_income_eligible},
+                    "msp_asset_eligible": {f"{PERIOD}-01": msp_asset_eligible},
+                }
+            },
+            "households": {"household": {"members": ["person"]}},
+            "tax_units": {"tax_unit": {"members": ["person"]}},
+            "spm_units": {"spm_unit": {"members": ["person"]}},
+            "families": {"family": {"members": ["person"]}},
+            "marital_units": {"marital_unit": {"members": ["person"]}},
+        },
+    )
+
+
+def test_msp_part_b_premium_coverage_pays_standard_premium():
+    sim = make_simulation(
+        medicare_enrolled=True,
+        gross_part_b_premium=4_440,
+        base_part_b_premium=2_220,
+        msp_income_eligible=True,
+        msp_asset_eligible=True,
+    )
+
+    assert sim.calculate("msp_part_b_premium_coverage", PERIOD)[0] == pytest.approx(
+        2_220
+    )
+
+
+def test_medicare_part_b_premiums_preserve_only_irmaa_above_msp_support():
+    sim = make_simulation(
+        medicare_enrolled=True,
+        gross_part_b_premium=4_440,
+        base_part_b_premium=2_220,
+        msp_income_eligible=True,
+        msp_asset_eligible=True,
+    )
+
+    assert sim.calculate("medicare_part_b_premiums", PERIOD)[0] == pytest.approx(2_220)
+
+
+def test_medicare_part_b_premiums_are_zero_when_msp_covers_standard_premium():
+    sim = make_simulation(
+        medicare_enrolled=True,
+        gross_part_b_premium=2_220,
+        base_part_b_premium=2_220,
+        msp_income_eligible=True,
+        msp_asset_eligible=True,
+    )
+
+    assert sim.calculate("medicare_part_b_premiums", PERIOD)[0] == pytest.approx(0)
+
+
+def test_medicare_cost_uses_gross_part_b_before_msp_offset():
+    sim = Simulation(
+        tax_benefit_system=SYSTEM,
+        situation={
+            "people": {
+                "person": {
+                    "age": {PERIOD: 65},
+                    "medicare_enrolled": {PERIOD: True},
+                    "base_part_a_premium": {PERIOD: 0},
+                    "income_adjusted_part_b_premium": {PERIOD: 2_220},
+                    "base_part_b_premium": {PERIOD: 2_220},
+                    "msp_income_eligible": {f"{PERIOD}-01": True},
+                    "msp_asset_eligible": {f"{PERIOD}-01": True},
+                }
+            },
+            "households": {"household": {"members": ["person"]}},
+            "tax_units": {"tax_unit": {"members": ["person"]}},
+            "spm_units": {"spm_unit": {"members": ["person"]}},
+            "families": {"family": {"members": ["person"]}},
+            "marital_units": {"marital_unit": {"members": ["person"]}},
+        },
+    )
+
+    assert sim.calculate("medicare_part_b_premiums", PERIOD)[0] == pytest.approx(0)
+    assert sim.calculate("medicare_cost", PERIOD)[0] == pytest.approx(12_280)
+
+
+def test_medicare_part_b_premiums_are_zero_when_not_enrolled():
+    sim = make_simulation(
+        medicare_enrolled=False,
+        gross_part_b_premium=2_220,
+        base_part_b_premium=2_220,
+        msp_income_eligible=True,
+        msp_asset_eligible=True,
+    )
+
+    assert sim.calculate("msp_part_b_premium_coverage", PERIOD)[0] == pytest.approx(0)
+    assert sim.calculate("medicare_part_b_premiums", PERIOD)[0] == pytest.approx(0)
+
+
+def test_legacy_medicare_part_b_input_uprates_forward():
+    sim = Simulation(
+        tax_benefit_system=SYSTEM,
+        situation={
+            "people": {
+                "person": {
+                    "age": {"2024": 65},
+                    "medicare_part_b_premiums": {"2024": 1_000},
+                }
+            },
+            "households": {"household": {"members": ["person"]}},
+            "tax_units": {"tax_unit": {"members": ["person"]}},
+            "spm_units": {"spm_unit": {"members": ["person"]}},
+            "families": {"family": {"members": ["person"]}},
+            "marital_units": {"marital_unit": {"members": ["person"]}},
+        },
+    )
+
+    assert sim.calculate("medicare_part_b_premiums", "2025")[0] == pytest.approx(
+        1_030.8833,
+        abs=1e-3,
+    )
+
+
+def test_msp_part_b_premium_coverage_scales_with_eligible_months():
+    monthly_eligibility = {
+        f"{PERIOD}-{month:02d}": month <= 3 for month in range(1, 13)
+    }
+    sim = Simulation(
+        tax_benefit_system=SYSTEM,
+        situation={
+            "people": {
+                "person": {
+                    "age": {PERIOD: 65},
+                    "medicare_enrolled": {PERIOD: True},
+                    "base_part_b_premium": {PERIOD: 2_220},
+                    "msp_income_eligible": monthly_eligibility,
+                    "msp_asset_eligible": monthly_eligibility,
+                }
+            },
+            "households": {"household": {"members": ["person"]}},
+            "tax_units": {"tax_unit": {"members": ["person"]}},
+            "spm_units": {"spm_unit": {"members": ["person"]}},
+            "families": {"family": {"members": ["person"]}},
+            "marital_units": {"marital_unit": {"members": ["person"]}},
+        },
+    )
+
+    assert sim.calculate("msp_part_b_premium_coverage", PERIOD)[0] == pytest.approx(
+        555,
+        abs=1e-6,
+    )
+
+
+def test_medicare_part_b_premiums_do_not_depend_on_calculation_order():
+    no_msp_eligibility = {
+        f"{year}-{month:02d}": False
+        for year in ("2025", "2026")
+        for month in range(1, 13)
+    }
+    situation = {
+        "people": {
+            "person": {
+                "age": {"2025": 65, "2026": 66},
+                "medicare_enrolled": {"2025": True, "2026": True},
+                "income_adjusted_part_b_premium": {"2025": 2_220, "2026": 2_220},
+                "base_part_b_premium": {"2025": 2_220, "2026": 2_220},
+                "msp_income_eligible": no_msp_eligibility,
+                "msp_asset_eligible": no_msp_eligibility,
+            }
+        },
+        "households": {"household": {"members": ["person"]}},
+        "tax_units": {"tax_unit": {"members": ["person"]}},
+        "spm_units": {"spm_unit": {"members": ["person"]}},
+        "families": {"family": {"members": ["person"]}},
+        "marital_units": {"marital_unit": {"members": ["person"]}},
+    }
+
+    ordered_sim = Simulation(tax_benefit_system=SYSTEM, situation=situation)
+    ordered_sim.calculate("medicare_part_b_premiums", "2025")
+    ordered_result = ordered_sim.calculate("medicare_part_b_premiums", "2026")[0]
+
+    fresh_sim = Simulation(tax_benefit_system=SYSTEM, situation=situation)
+    fresh_result = fresh_sim.calculate("medicare_part_b_premiums", "2026")[0]
+
+    assert ordered_result == pytest.approx(fresh_result)
+    assert ordered_result == pytest.approx(2_220)
+
+
+def test_income_adjusted_part_b_premium_handles_direct_filing_status_inputs():
+    sim = Simulation(
+        tax_benefit_system=SYSTEM,
+        situation={
+            "people": {
+                "person_1": {
+                    "age": {PERIOD: 65},
+                    "base_part_b_premium": {PERIOD: 2_220},
+                    "is_medicare_eligible": {PERIOD: True},
+                    "tax_exempt_interest_income": {"2023": 0},
+                },
+                "person_2": {
+                    "age": {PERIOD: 65},
+                    "base_part_b_premium": {PERIOD: 2_220},
+                    "is_medicare_eligible": {PERIOD: True},
+                    "tax_exempt_interest_income": {"2023": 0},
+                },
+                "person_3": {
+                    "age": {PERIOD: 65},
+                    "base_part_b_premium": {PERIOD: 2_220},
+                    "is_medicare_eligible": {PERIOD: True},
+                    "tax_exempt_interest_income": {"2023": 0},
+                },
+            },
+            "households": {
+                "household": {"members": ["person_1", "person_2", "person_3"]}
+            },
+            "tax_units": {
+                "joint_tax_unit": {
+                    "members": ["person_1", "person_2"],
+                    "filing_status": {PERIOD: "JOINT"},
+                    "adjusted_gross_income": {"2023": 1_000_000},
+                },
+                "single_tax_unit": {
+                    "members": ["person_3"],
+                    "filing_status": {PERIOD: "SINGLE"},
+                    "adjusted_gross_income": {"2023": 50_000},
+                },
+            },
+            "spm_units": {
+                "spm_unit": {"members": ["person_1", "person_2", "person_3"]}
+            },
+            "families": {"family": {"members": ["person_1", "person_2", "person_3"]}},
+            "marital_units": {
+                "marital_unit_1": {"members": ["person_1", "person_2"]},
+                "marital_unit_2": {"members": ["person_3"]},
+            },
+        },
+    )
+
+    result = sim.calculate("income_adjusted_part_b_premium", PERIOD)
+    assert result[0] == pytest.approx(7_546.8)
+    assert result[1] == pytest.approx(7_546.8)
+    assert result[2] == pytest.approx(2_220)

policyengine_us/tests/policy/baseline/gov/states/mi/tax/income/credits/homestead_property_tax/integration.yaml

@@ -198,6 +198,7 @@
     employment_income: 56_000
     real_estate_taxes: 2_500
     age: 66
+    medicare_part_b_premiums: 0
     state_code: MI
   output: # (2500 - 56000 * 0.032) * 0.6 * 0.5
     mi_homestead_property_tax_credit_countable_property_tax: 2_500

policyengine_us/tests/policy/baseline/gov/states/mi/tax/income/integration.yaml

@@ -5,6 +5,7 @@
     people:
       person1:
         age: 67
+        medicare_part_b_premiums: 0
         employment_income: 10_010
         taxable_interest_income: 11_010
         taxable_private_pension_income: 7_000