Value QMB cost sharing at Medicaid's CMS-64 spending per QMB

changelog.d/qmb-cost-sharing-calibration.fixed.md

@@ -0,0 +1 @@
+Value QMB cost sharing at Medicaid's spending per Qualified Medicare Beneficiary from CMS-64 line 17D ($137.70 a year in FY 2024), replacing 20 percent of all Medicare spending per enrollee, and remove the unused `gov.hhs.medicare.savings_programs.qmb.cost_sharing_rate` parameter.

policyengine_us/parameters/calibration/gov/hhs/medicare/savings_programs/qmb_cost_sharing_per_enrollee.yaml

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+description: Medicaid spending on Medicare deductibles and coinsurance for Qualified Medicare Beneficiaries, per Qualified Medicare Beneficiary enrollee per year.
+# Each value is a federal fiscal year (October through September): national
+# CMS-64 net expenditures on line 17D, "Coinsurance" (total computable), over
+# Qualified Medicare Beneficiary person-years (QMB only plus QMB plus) from CMS
+# Program Statistics. Fiscal year Y takes 0.25 times calendar year Y-1 and
+# 0.75 times calendar year Y person-years. The latest value holds afterwards.
+values:
+  2014-10-01: 145.14 # FY 2015: $964,276,592 / 6,643,568.5
+  2015-10-01: 160.07 # FY 2016: $1,088,990,259 / 6,803,362.5
+  2016-10-01: 149.87 # FY 2017: $1,044,519,254 / 6,969,459.1
+  2017-10-01: 143.55 # FY 2018: $1,023,074,055 / 7,126,922.3
+  2018-10-01: 142.54 # FY 2019: $1,036,646,026 / 7,272,591.8
+  2019-10-01: 138.65 # FY 2020: $1,040,603,350 / 7,505,377.9
+  2020-10-01: 133.70 # FY 2021: $1,046,566,216 / 7,827,817.8
+  2021-10-01: 128.05 # FY 2022: $1,037,693,614 / 8,103,524.3
+  2022-10-01: 132.92 # FY 2023: $1,118,400,599 / 8,413,952.4
+  2023-10-01: 137.70 # FY 2024: $1,153,227,651 / 8,374,811.6
+
+metadata:
+  unit: currency-USD
+  period: year
+  label: Medicaid spending on QMB Medicare cost sharing per enrollee
+  reference:
+    - title: CMS - Medicaid Financial Management Reports, FY 2015 to FY 2024 net expenditures, National Totals, line "Coinsurance"
+      href: https://www.medicaid.gov/medicaid/financial-management/state-expenditure-reporting-for-medicaid-chip/expenditure-reports-mbescbes
+    - title: CMS-64.9 Base category of service line definitions - line 17D, Coinsurance and Deductibles for QMBs under section 1905(p)(3)
+      href: https://www.medicaid.gov/medicaid/downloads/cms-649-base-category-of-services-definition.pdf#page=18
+    - title: CMS Program Statistics - Medicare-Medicaid Dual Enrollment, table MDCR ENROLL AB 40 (QMB only and QMB plus person-years)
+      href: https://data.cms.gov/summary-statistics-on-beneficiary-enrollment/medicare-and-medicaid-reports/cms-program-statistics-medicare-medicaid-dual-enrollment
+    - title: MACPAC - MACStats December 2024, Exhibit 17 (FY 2023 Medicare premiums and coinsurance, the sum of CMS-64 lines 17A to 17D)
+      href: https://www.macpac.gov/wp-content/uploads/2024/12/MACSTATS_Dec2024_WEB-508.pdf#page=61
+    - title: 42 U.S.C. 1396d(p)(3) - Medicare cost-sharing definition
+      href: https://www.law.cornell.edu/uscode/text/42/1396d#p_3

policyengine_us/tests/core/test_qmb_cost_sharing_per_enrollee.py

@@ -0,0 +1,243 @@
+"""Medicaid spending on Medicare cost sharing per Qualified Medicare Beneficiary.
+
+``calibration.gov.hhs.medicare.savings_programs.qmb_cost_sharing_per_enrollee``
+values QMB coverage of Medicare deductibles and coinsurance at what Medicaid
+spends on it. Each federal fiscal year's value is national CMS-64 net
+expenditure on line 17D, "Coinsurance and Deductibles", which holds "Medicare
+deductibles and coinsurance required to be paid for QMBs under §1905(p)(3)"
+(CMS-64.9 Base line definitions, page 18), over QMB person-years from CMS
+Program Statistics (QMB only plus QMB plus, table MDCR ENROLL AB 40). Fiscal
+year Y runs October Y-1 to September Y, so its person-years are 0.25 times
+calendar year Y-1 plus 0.75 times calendar year Y, and its value is dated
+October 1 of Y-1. ``qmb_cost_sharing`` pays a QMB a twelfth of it each month.
+
+Invariants:
+
+1. Transcription: each value is the line 17D total over fiscal-year QMB
+   person-years, rounded to the cent, recomputed here from the published
+   totals.
+2. Cross-source: line 17D equals MACStats December 2024 Exhibit 17's FY 2023
+   "Medicare premiums and coinsurance" column ($27,587 million) less CMS-64
+   lines 17A to 17C1 for the same year.
+3. Level: every value is positive and under a fifth of the fee-for-service
+   Part A and Part B cost sharing that QMBs incurred per QMB person-year in
+   calendar 2022, $1,139 (MedPAC and MACPAC duals data book, December 2025,
+   Table 6, over the same person-years). The series is what Medicaid pays,
+   not the cost sharing Medicare charges: 42 U.S.C. 1396a(n)(2) does not
+   require a state to pay once Medicare's payment reaches its Medicaid rate.
+4. Dating: each date reads the value of the fiscal year it falls in, and every
+   date after September 2024 reads the FY 2024 value.
+5. Consumers: a QMB's monthly ``qmb_cost_sharing`` is the value in force that
+   month over 12, other categories get zero, and a calendar year sums to nine
+   twelfths of one fiscal year's value plus three twelfths of the next.
+   ``msp_federal_cost`` plus ``msp_state_cost`` equals ``msp_cost`` for QMB and
+   SLMB, and a full Medicaid enrollee has no separate MSP cost.
+"""
+
+from decimal import ROUND_HALF_UP, Decimal
+
+import pytest
+from hypothesis import given, settings
+from hypothesis import strategies as st
+from policyengine_core.parameters.operations.get_parameter import get_parameter
+
+from policyengine_us import Simulation
+from policyengine_us.system import system
+
+SERIES = "calibration.gov.hhs.medicare.savings_programs.qmb_cost_sharing_per_enrollee"
+FIRST_FY, LAST_FY = 2015, 2024
+FISCAL_YEARS = range(FIRST_FY, LAST_FY + 1)
+
+# CMS Medicaid Financial Management Report net expenditures, Medical
+# Assistance Program, "MAP - National Totals" sheet, line "Coinsurance"
+# (CMS-64.9 line 17D), total computable, from financial-management-report-
+# fy<YEAR>.zip on medicaid.gov.
+LINE_17D = {
+    2015: 964_276_592,
+    2016: 1_088_990_259,
+    2017: 1_044_519_254,
+    2018: 1_023_074_055,
+    2019: 1_036_646_026,
+    2020: 1_040_603_350,
+    2021: 1_046_566_216,
+    2022: 1_037_693_614,
+    2023: 1_118_400_599,
+    2024: 1_153_227_651,
+}
+# FY 2023 CMS-64 lines 17A (Medicare - Part A), 17B (Medicare - Part B) and
+# 17C1 (120% - 134% Of Poverty), same sheet.
+FY2023_PREMIUM_LINES = (4_467_995_163, 20_740_509_880, 1_260_062_080)
+# MACStats December 2024, Exhibit 17, Total row, "Medicare premiums and
+# coinsurance" column, FY 2023, millions.
+MACSTATS_FY2023_MEDICARE_PREMIUMS_AND_COINSURANCE = 27_587
+# CMS Program Statistics, Medicare-Medicaid Enrollment, table MDCR ENROLL AB
+# 40, all areas, person-years as (QMB plus, QMB only). 2014-2016 from the
+# 2017 release, 2017-2024 from the 2022 and 2024 releases.
+QMB_PERSON_YEARS = {
+    2014: (5_188_112, 1_329_131),
+    2015: (5_302_665, 1_383_012),
+    2016: (5_394_679, 1_447_912),
+    2017: (5_491_307.666665925, 1_520_440.750000014),
+    2018: (5_612_836.249999335, 1_552_477.333333389),
+    2019: (5_740_930.41666614, 1_567_420.833333381),
+    2020: (5_916_824.416666307, 1_654_229.083333384),
+    2021: (6_204_436.916666491, 1_708_968.916666722),
+    2022: (6_424_476.916666286, 1_742_420.166666717),
+    2023: (6_767_803.583332852, 1_728_500.583333357),
+    2024: (6_586_884.583332959, 1_747_429.499999969),
+}
+# MedPAC and MACPAC, Data book: Beneficiaries dually eligible for Medicare and
+# Medicaid, December 2025, Table 6: fee-for-service Part A and Part B cost
+# sharing incurred in calendar 2022, billions, QMB plus and QMB only.
+CY2022_QMB_FFS_COST_SHARING_INCURRED = 8.1e9 + 1.2e9
+
+
+def _series(date):
+    return get_parameter(system.parameters, SERIES)(date)
+
+
+def _fiscal_year_value(fiscal_year):
+    return _series(f"{fiscal_year - 1}-10-01")
+
+
+def _fiscal_year_person_years(fiscal_year):
+    previous = sum(QMB_PERSON_YEARS[fiscal_year - 1])
+    current = sum(QMB_PERSON_YEARS[fiscal_year])
+    return 0.25 * previous + 0.75 * current
+
+
+def _expected(fiscal_year):
+    ratio = LINE_17D[fiscal_year] / _fiscal_year_person_years(fiscal_year)
+    return float(Decimal(ratio).quantize(Decimal("0.01"), rounding=ROUND_HALF_UP))
+
+
+@pytest.mark.parametrize("fiscal_year", FISCAL_YEARS)
+def test_value_is_line_17d_over_qmb_person_years(fiscal_year):
+    assert _fiscal_year_value(fiscal_year) == _expected(fiscal_year)
+
+
+def test_line_17d_is_macstats_medicare_column_less_premium_lines():
+    total = LINE_17D[2023] + sum(FY2023_PREMIUM_LINES)
+    assert round(total / 1e6) == MACSTATS_FY2023_MEDICARE_PREMIUMS_AND_COINSURANCE
+
+
+@pytest.mark.parametrize("fiscal_year", FISCAL_YEARS)
+def test_value_is_below_cost_sharing_incurred_per_qmb(fiscal_year):
+    incurred_per_qmb = CY2022_QMB_FFS_COST_SHARING_INCURRED / sum(
+        QMB_PERSON_YEARS[2022]
+    )
+    assert 0 < _fiscal_year_value(fiscal_year) < incurred_per_qmb / 5
+
+
+@given(
+    st.integers(FIRST_FY, LAST_FY),
+    st.integers(1, 12),
+    st.integers(1, 28),
+)
+def test_each_date_reads_its_fiscal_year(fiscal_year, month, day):
+    calendar_year = fiscal_year - 1 if month >= 10 else fiscal_year
+    if calendar_year < FIRST_FY - 1 or (calendar_year, month) < (FIRST_FY - 1, 10):
+        return
+    date = f"{calendar_year}-{month:02d}-{day:02d}"
+    assert _series(date) == _fiscal_year_value(fiscal_year)
+
+
+@given(st.integers(2024, 2100), st.integers(1, 12), st.integers(1, 28))
+def test_dates_after_fy_2024_hold_its_value(year, month, day):
+    if year == 2024 and month < 10:
+        return
+    assert _series(f"{year}-{month:02d}-{day:02d}") == _fiscal_year_value(LAST_FY)
+
+
+def _person_simulation(year, person):
+    members = ["person"]
+    return Simulation(
+        situation={
+            "people": {"person": person},
+            "tax_units": {"tax_unit": {"members": members}},
+            "spm_units": {"spm_unit": {"members": members}},
+            "families": {"family": {"members": members}},
+            "marital_units": {"marital_unit": {"members": members}},
+            "households": {
+                "household": {"members": members, "state_code": {year: "CA"}}
+            },
+        }
+    )
+
+
+CATEGORIES = ("QMB", "SLMB", "QI", "NONE")
+
+
+@settings(max_examples=25, deadline=None)
+@given(st.integers(2015, 2035), st.integers(1, 12), st.sampled_from(CATEGORIES))
+def test_qmb_gets_a_twelfth_of_the_value_in_force(year, month, category):
+    period = f"{year}-{month:02d}"
+    simulation = _person_simulation(year, {"msp_category": {period: category}})
+    paid = simulation.calculate("qmb_cost_sharing", period)[0]
+    expected = _series(f"{period}-01") / 12 if category == "QMB" else 0
+    # Variables are float32.
+    assert paid == pytest.approx(expected, rel=1e-6, abs=1e-6)
+
+
+@settings(max_examples=15, deadline=None)
+@given(st.integers(2015, 2035))
+def test_calendar_year_sums_nine_and_three_twelfths(year):
+    simulation = _person_simulation(year, {"msp_category": {year: "QMB"}})
+    annual = sum(
+        simulation.calculate("qmb_cost_sharing", f"{year}-{month:02d}")[0]
+        for month in range(1, 13)
+    )
+    expected = (9 * _series(f"{year}-01-01") + 3 * _series(f"{year}-10-01")) / 12
+    assert annual == pytest.approx(expected, rel=1e-6)
+
+
+@settings(max_examples=25, deadline=None)
+@given(
+    st.integers(2015, 2035),
+    st.sampled_from(("QMB", "SLMB", "QI")),
+    st.sampled_from(("CA", "AL", "NY", "MS", "DC")),
+    st.floats(0, 6_000, allow_nan=False),
+    st.floats(0, 10_000, allow_nan=False),
+    st.booleans(),
+)
+def test_msp_cost_splits_between_federal_and_state(
+    year, category, state, part_a_premium, part_b_premium, medicaid_enrolled
+):
+    members = ["person"]
+    simulation = Simulation(
+        situation={
+            "people": {
+                "person": {
+                    "age": {year: 67},
+                    "is_medicare_eligible": {year: True},
+                    "medicaid_enrolled": {year: medicaid_enrolled},
+                    "msp_category": {year: category},
+                    "base_part_a_premium": {year: part_a_premium},
+                    "base_part_b_premium": {year: part_b_premium},
+                }
+            },
+            "tax_units": {"tax_unit": {"members": members}},
+            "spm_units": {"spm_unit": {"members": members}},
+            "families": {"family": {"members": members}},
+            "marital_units": {"marital_unit": {"members": members}},
+            "households": {
+                "household": {"members": members, "state_code": {year: state}}
+            },
+        }
+    )
+    total = simulation.calculate("msp_cost", year)[0]
+    federal = simulation.calculate("msp_federal_cost", year)[0]
+    state_cost = simulation.calculate("msp_state_cost", year)[0]
+    if medicaid_enrolled:
+        assert total == federal == state_cost == 0
+        return
+    cost_sharing = sum(
+        simulation.calculate("qmb_cost_sharing", f"{year}-{month:02d}")[0]
+        for month in range(1, 13)
+    )
+    premiums = part_b_premium + (part_a_premium if category == "QMB" else 0)
+    assert total == pytest.approx(premiums + cost_sharing, rel=1e-5, abs=0.01)
+    assert federal + state_cost == pytest.approx(total, rel=1e-5, abs=0.01)
+    assert 0 <= federal <= total + 0.01
+    if category == "QI":
+        assert state_cost == pytest.approx(0, abs=0.01)

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

@@ -11,8 +11,8 @@
     base_part_b_premium: 2_434.8
   output:
     # Part B premium: $202.90 * 12 = $2,434.80.
-    # QMB cost sharing: $14,500 * 20% = $2,900.
-    msp_cost: 5_334.8
+    # QMB cost sharing: Medicaid's $137.70 a year per QMB (FY 2024, held).
+    msp_cost: 2_572.5
 
 - name: Case 2, SLMB MSP-only beneficiary receives Part B premium value.
   period: 2026
@@ -55,3 +55,20 @@
     base_part_b_premium: 2_434.8
   output:
     msp_cost: 0
+
+- name: Case 5, QMB cost sharing switches fiscal year in October.
+  period: 2023
+  absolute_error_margin: 0.01
+  input:
+    state_code: CA
+    age: 67
+    is_medicare_eligible: true
+    medicaid_enrolled: false
+    msp_category: QMB
+    base_part_a_premium: 0
+    base_part_b_premium: 1_978.8
+  output:
+    # Part B premium: $164.90 * 12 = $1,978.80. QMB cost sharing: nine
+    # months of FY 2023 ($132.92 / 12) and three of FY 2024 ($137.70 / 12)
+    # = $99.69 + $34.425 = $134.115.
+    msp_cost: 2_112.915

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

@@ -10,9 +10,10 @@
     base_part_a_premium: 0
     base_part_b_premium: 2_434.8
   output:
-    # CA regular FMAP is 50%; total MSP cost is $5,334.80.
-    msp_federal_cost: 2_667.4
-    msp_state_cost: 2_667.4
+    # CA regular FMAP is 50%; total MSP cost is $2,434.80 Part B premium
+    # plus $137.70 QMB cost sharing = $2,572.50.
+    msp_federal_cost: 1_286.25
+    msp_state_cost: 1_286.25
 
 - name: Case 2, QI cost is federally financed within allocation.
   period: 2026

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

@@ -1,11 +1,12 @@
-- name: Case 1, QMB cost sharing uses the monthly Medicare cost approximation.
+- name: Case 1, QMB cost sharing is a twelfth of Medicaid's annual spending per QMB.
   period: 2026-01
-  absolute_error_margin: 0.01
+  absolute_error_margin: 0.001
   input:
     msp_category: QMB
   output:
-    # $14,500 annual Medicare per-capita cost / 12 * 20%.
-    qmb_cost_sharing: 241.67
+    # FY 2024 CMS-64 line 17D, $1,153,227,651, over 8,374,811.6 QMB
+    # person-years is $137.70 a year, held after FY 2024; / 12 = $11.475.
+    qmb_cost_sharing: 11.475
 
 - name: Case 2, non-QMB MSP categories do not receive QMB cost sharing.
   period: 2026-01
@@ -14,3 +15,21 @@
     msp_category: SLMB
   output:
     qmb_cost_sharing: 0
+
+- name: Case 3, September 2023 uses the fiscal year 2023 value.
+  period: 2023-09
+  absolute_error_margin: 0.001
+  input:
+    msp_category: QMB
+  output:
+    # FY 2023: $1,118,400,599 / 8,413,952.4 = $132.92 a year; / 12.
+    qmb_cost_sharing: 11.076667
+
+- name: Case 4, October 2023 starts the fiscal year 2024 value.
+  period: 2023-10
+  absolute_error_margin: 0.001
+  input:
+    msp_category: QMB
+  output:
+    # FY 2024: $137.70 a year; / 12.
+    qmb_cost_sharing: 11.475

policyengine_us/tests/policy/baseline/household/income/person/federal_and_state_benefit_cost.yaml

@@ -84,5 +84,7 @@
     base_part_a_premium: 0
     base_part_b_premium: 2_434.8
   output:
-    federal_benefit_cost: 2_667.4
-    state_benefit_cost: 2_667.4
+    # MSP cost: $2,434.80 Part B premium + $137.70 QMB cost sharing =
+    # $2,572.50, split at CA's 50% FMAP.
+    federal_benefit_cost: 1_286.25
+    state_benefit_cost: 1_286.25