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

[MaxGhenis]

Summary

qmb_cost_sharing valued a Qualified Medicare Beneficiary's coverage of Medicare deductibles and coinsurance at 20% of calibration.gov.hhs.medicare.per_capita_cost: $14,500 × 20% = $2,900 a year on main, or $18,983 × 20% = $3,797 in 2026 under #10107. That base includes Part D (about 15% of Medicare spending; 2026 Trustees Report Table II.B1: $181.5B of $1,210.1B in 2025) and administration. QMB covers neither: 42 U.S.C. 1396d(p)(3) limits it to Part A and B premiums, deductibles and coinsurance. The formula also ignores lesser-of payment policies. 42 U.S.C. 1396a(n)(2) does not require a state to pay cost sharing once Medicare's payment reaches the state's Medicaid rate, and 37 to 41 states limit payment this way, depending on the service (MACPAC August 2025 brief, Table 1).

This PR values QMB cost sharing at what Medicaid actually spends on it per QMB. That is CMS-64 line 17D over QMB person-years:

• Line 17D: "Medicare deductibles and coinsurance required to be paid for QMBs under §1905 (p)(3)" (CMS-64.9 Base line definitions, p. 18).
• Spending: national net expenditures, total computable, from CMS's Financial Management Reports, FY 2015–2024.
• Enrollment: QMB-only plus QMB-plus person-years from CMS Program Statistics (Medicare-Medicaid Enrollment table AB 40).
• Fiscal-year alignment: FY Y's enrollment is 0.25 × CY Y−1 + 0.75 × CY Y.

FY	Line 17D	QMB person-years	Per QMB per year
2015	$964,276,592	6,643,569	$145.14
2016	$1,088,990,259	6,803,363	$160.07
2017	$1,044,519,254	6,969,459	$149.87
2018	$1,023,074,055	7,126,922	$143.55
2019	$1,036,646,026	7,272,592	$142.54
2020	$1,040,603,350	7,505,378	$138.65
2021	$1,046,566,216	7,827,818	$133.70
2022	$1,037,693,614	8,103,524	$128.05
2023	$1,118,400,599	8,413,952	$132.92
2024	$1,153,227,651	8,374,812	$137.70

What changed

• New parameter. calibration.gov.hhs.medicare.savings_programs.qmb_cost_sharing_per_enrollee holds the series. Each value is dated October 1, the first day of its fiscal year, the same convention as gov.hhs.medicaid.cost_share.fmap. The FY 2024 value holds afterwards. The series fell 1.9% a year from FY 2016 to FY 2024, then rose 3.8% and 3.6% in the last two years, so there is no trend to project.
• Formula. qmb_cost_sharing now pays a QMB one twelfth of the value in force each month. It no longer reads per_capita_cost. A calendar year is therefore nine twelfths of one fiscal year's value plus three twelfths of the next.
• Removed. The unused gov.hhs.medicare.savings_programs.qmb.cost_sharing_rate is deleted; qmb_cost_sharing was its only reader.

Why a dollar series, not a rate on a narrower base

The task allowed basing a rate on Part A/B spending only. No constant rate on any Medicare spending base reproduces the published series:

• All Parts (NHE Table 17 Medicare spending per enrollee, Use CMS Medicare spending per enrollee for the Medicare per capita cost #10107's series): the implied rate falls from 1.32% in FY 2016 ($160.07 / $12,119) to 0.82% in FY 2024 ($137.70 / $16,779).
• Part A + Part B only (2026 Trustees Report Table V.D1): HI plus Part B per beneficiary cost was $10,766 in 2016 and $14,989 in 2024. The implied rate falls from 1.49% to 0.92%.

Either way the rate would have to fall 38% in eight years.

Verification of the figure

• In every year, state rows sum exactly to the national row.
• The FY 2016 national value matches data.medicaid.gov's "Medicaid Financial Management Data – National Totals" exactly ($1,088,990,259).
• For FY 2023, lines 17A + 17B + 17C1 + 17D = $27,586,967,722. That matches MACStats December 2024 Exhibit 17's "Medicare premiums and coinsurance" total of $27,587 million.
• MACPAC treats line 17D as Medicaid's QMB cost-sharing spending: the MACStats technical guide (Exhibit 51, note 4) distributes the "CMS-64 amounts for QMBs" across service categories.

Limits of the figure, and comparators

• States differ in how they report. 22 to 25 states report a nonzero line 17D. California, New York, Texas, Pennsylvania, Georgia, Alabama and others report $0, so they presumably book crossover payments under service lines. Per QMB, the reporting states average $370 to $398 (FY 2022–2024), but they range from $1–2 (Illinois) to $2,069 (Arkansas). Arkansas's figure per fee-for-service QMB exceeds the whole fee-for-service liability per QMB, so the line is not clean state by state either. Reporting differences push the national ratio low.
• QMB-only versus QMB-plus. The model applies this value only to QMB-only people, because msp_cost is zero for Medicaid enrollees. QMB-only enrollees incur less cost sharing per person-year than QMB-plus enrollees: $689 versus $1,261 in CY 2022, from MedPAC–MACPAC Table 6 over CMS person-years. That pushes the other way. The per-QMB average also includes institutionalized QMBs, whom the CPS-based microdata exclude. SNF copayments (days 21–100) are $1.3B of the $8.1B QMB-plus liability in Table 6, but only $0.1B of the $1.2B QMB-only liability.
• Upper reference, cost sharing incurred. The December 2025 MedPAC–MACPAC duals data book (Table 6) puts fee-for-service Part A and B cost sharing incurred by QMB-only beneficiaries at $1.2B in CY 2022. That is $689 per QMB-only person-year, or $2,269 per fee-for-service QMB-only person-year. The data book says these amounts "do not reflect the actual cost-sharing amounts paid to providers by beneficiaries, Medicaid, or other third parties." The old $2,900 exceeded the $689 average liability by a factor of four.
• Payment shares. In lesser-of states, Medicaid paid 11% to 93% of evaluation-and-management cost sharing, mostly under 50% (Haber et al. 2014, cited in MACPAC's March 2015 report, chapter 6).
• CMS actuarial assumption. The 2023 Medicare Savings Program rule's impact analysis assumed "about $5,000 per enrollee per year for 2023" for Part B premium and cost-sharing assistance to newly enrolled SSI recipients (88 FR 65264). That leaves about $3,000 of cost sharing after the $1,978.80 Part B premium. It is an assumption for a sicker population, not a measured payment.

Invariants (tested)

policyengine_us/tests/core/test_qmb_cost_sharing_per_enrollee.py:

1. Transcription: each value equals line 17D over fiscal-year QMB person-years, rounded to the cent, recomputed from the published totals in the test.
2. Cross-source: line 17D plus FY 2023 lines 17A–17C1 equals MACStats Exhibit 17's $27,587 million.
3. Level: every value is positive and under a fifth of CY 2022's fee-for-service cost sharing incurred per QMB person-year ($1,139).
4. Dating (Hypothesis): every date reads its own fiscal year's value, and every date from October 2024 to 2100 reads the FY 2024 value.
5. Consumers (Hypothesis): a QMB's monthly qmb_cost_sharing is the value in force over 12, and SLMB, QI and no category get zero. A calendar year sums to 9/12 of one fiscal year's value plus 3/12 of the next. For QMB, SLMB and QI across states, premiums and Medicaid enrollment:
   • msp_cost equals the premiums plus the summed cost sharing;
   • msp_federal_cost + msp_state_cost equals msp_cost;
   • QI has no state cost;
   • a Medicaid enrollee has no MSP cost.

YAML: four expectations move from $2,900 to $137.70 of QMB cost sharing: qmb_cost_sharing, msp_cost, msp_federal_and_state_cost and federal_and_state_benefit_cost. New cases cover September and October 2023 and a 2023 msp_cost that straddles the fiscal-year boundary.

Impact

PENDING: full-population microsim, base upstream/main 065d0e9 vs this PR, 2026, on the default dataset. Variables: msp_cost, msp_federal_cost, msp_state_cost, federal_benefit_cost, state_benefit_cost, healthcare_benefit_value, household_health_benefits, household_net_income.

household_net_income and SPM resources do not include msp_cost. Health benefits enter net income only when gov.simulation.include_health_benefits_in_net_income is on. So poverty and net income should not move.

Interaction with #10107

#10107 replaces per_capita_cost. After this PR, QMB cost sharing no longer depends on it. #10107's edits to qmb_cost_sharing.yaml, msp_cost.yaml, msp_federal_and_state_cost.yaml and federal_and_state_benefit_cost.yaml, and its test_qmb_cost_sharing_is_the_qmb_rate_of_monthly_spending, are superseded here. Whichever PR merges second takes these versions. #10107's session has been told.

Tests run

• policyengine-core test on gov/hhs/medicare/savings_programs, household/income/person/federal_and_state_benefit_cost.yaml, household/healthcare_benefit_value.yaml and household/household_health_benefits.yaml: 111 passed.
• pytest on tests/core/test_qmb_cost_sharing_per_enrollee.py, test_part_b_msp_offset.py, and the parameter and reference-URL code-health tests: 146 passed.

axiom: n/a: calibration (an empirical spending figure that approximates claims-level cost sharing, not a rule)

Evidence, with source files, SHA256 sums, extraction scripts and notes: ~/reviews/qmb-cost-sharing-2026-10/.

🤖 Generated with Claude Code

[MaxGhenis]

The CI run on this pull request was cancelled at 23:27Z on 2026-10-11 to free the organization's shared GitHub runners for an urgent fix in another repository. The US + core hub will re-run it automatically (cancelled jobs only; jobs that had passed are kept). Nothing in this pull request changed. Please don't push or reopen just to restart CI.