Implement Michigan State Supplementary Payment (SSP)

[hua7450]

Summary

Implements Michigan's State Supplementary Payment (SSP) — a state-funded supplement to federal SSI covering all six living-arrangement categories (Independent Living, Household of Another, Domiciliary Care, Personal Care, Home for the Aged, and Institution).

Closes #8175

Regulatory Authority

• BEM 660 (primary state regulation governing State SSI Payments)
• RFT 248 — SSI Payment Levels (rate schedule, current + historical Wayback snapshots)
• MCL 400.10 (Social Welfare Act 1939 PA 280, statutory basis)
• POMS SI CHI01415.001 (split federal/state administration)
• BEM 220 (Michigan residence requirements)
• SSA 2011 State Assistance Programs — Michigan baseline (frozen-rate confirmation, payment calculation method)

Program Overview

• Administration: SPLIT per BEM 660 p.1
  • MDHHS issues SSPs for Independent Living and Household of Another (paid quarterly in March, June, September, December per RFS 106). BEM 660 requires "regular first-of-month federal SSI benefit" for these.
  • SSA issues the state-funded benefit for Adult Foster Care (Domiciliary, Personal), Home for the Aged, and Institution categories — rolled into the monthly federal SSI check.
• Funding: State funds (both administration and assistance) per SSA 2011 Michigan baseline
• Current caseload: 248,803 SSI recipients in Michigan (Dec 2024, SSA SSI Recipients by State and County 2024); $185.1M in payments for December 2024

Eligibility (Two-Track Gate)

Michigan's split administration drives a two-track eligibility gate, grounded in BEM 660 + the SSA 2011 baseline:

Category	Administering agency	Eligibility gate	Source
Independent Living	MDHHS	ssi > 0 (regular federal SSI receipt)	BEM 660 p.1
Household of Another	MDHHS	ssi > 0 (regular federal SSI receipt)	BEM 660 p.1
Domiciliary Care	SSA	is_ssi_eligible + spillover	SSA 2011 baseline
Personal Care	SSA	is_ssi_eligible + spillover	SSA 2011 baseline
Home for the Aged	SSA	is_ssi_eligible + spillover	SSA 2011 baseline
Institution	SSA	is_ssi_eligible + spillover	SSA 2011 baseline

Why the split: BEM 660 p.1 says MDHHS-issued SSPs are paid "only for those months the recipient received a regular first-of-month federal benefit." That requirement applies to IL + HoA (the MDHHS-administered categories). For SSA-administered facility categories, the SSA 2011 baseline payment calculation method governs: "Countable income is deducted first from the federal payment. Any income that remains to be counted after the federal payment has been reduced to zero is then deducted from the state supplementary payment." The spillover formula max_(0, base - max_(0, -uncapped_ssi)) in mi_ssp_person.py implements this.

Other requirements	Source	How Modeled
Must reside in Michigan	BEM 220	defined_for = StateCode.MI
Aged 65+, Blind, or Disabled	BEM 660	covered by SSI eligibility (categorical or actual receipt depending on branch)
§1619(a)/(b) recipients excluded	BEM 660 p.2	Not modeled — we don't track §1619 status at the moment
Eligible Child same as IL individual	RFT 248 p.2	Default living_arrangement = INDEPENDENT_LIVING covers this implicitly

Living Arrangement Bridging

The implementation uses two enum variables (Maine SSP pattern):

• mi_ssp_living_arrangement — user-provided input enum
• mi_ssp_payment_category — derived enum that overrides the input with ssi_federal_living_arrangement for shared categories:
  • MEDICAL_TREATMENT_FACILITY → INSTITUTION
  • ANOTHER_PERSONS_HOUSEHOLD → HOUSEHOLD_OF_ANOTHER
  • All other federal values → fall back to user input

This auto-routes federal living-arrangement classifications without forcing users to set the MI-specific enum, while preserving the MI-only Adult Foster Care / Home for the Aged categories that the federal enum doesn't represent.

Parameter lookups and downstream variables key on mi_ssp_payment_category.

Benefit Amounts (RFT 248 p.2)

Living arrangement	Individual	Couple (2026)
Independent Living	$14.00	$21.00
Household of Another	$9.33	$13.96
Domiciliary Care	$87.00	$671.00
Personal Care	$157.50	$812.00
Home for the Aged	$179.30	$855.60
Institution	$7.00	$14.00

Couple treatment: Separate couple rate (NOT 2× individual). Couple rate paid only when joint SSI claim AND both spouses eligible AND same living arrangement.

COLA: Individual amounts FROZEN at the same nominal values 2016-2026 (corroborated against SSA 2011 baseline Table 1 for IL, Personal Care, Home for the Aged, and Institution — same values 15+ years). Couple supplements for Domiciliary Care, Personal Care, and Home for the Aged adjust upward each year (verified historical schedule 2016 / 2020 / 2022 / 2024 / 2026) because they are computed against a moving target including the federal couple FBR. Independent Living, Household of Another, and Institution couple rates are also frozen.

Not Modeled (by design)

What	Source	Why Excluded
§1619(a)/(b) exclusion	BEM 660 p.2	We don't track §1619 SSI extension status at the moment
Mandatory 1973-grandfathered supplements	BEM 660 p.3, SSA 2011 baseline	Population is 0 per SSA Table 2
Code G/H essential person categories	SSA 2011 baseline	Population is 0 per SSA Table 2
Special needs (personal care, emergency relief, state DA)	SSA 2011 baseline	Separate programs
Quarterly disbursement timing (MDHHS pays Mar/Jun/Sep/Dec)	BEM 660 p.1, RFS 106	Modeled as monthly equivalent

Files Added

policyengine_us/
├── parameters/gov/states/mi/mdhhs/ssp/
│   └── payment/
│       ├── individual.yaml
│       └── couple.yaml
├── variables/gov/states/mi/mdhhs/ssp/
│   ├── mi_ssp.py
│   ├── mi_ssp_couple_amount.py
│   ├── mi_ssp_couple_eligible.py
│   ├── mi_ssp_eligible.py
│   ├── mi_ssp_individual_amount.py
│   ├── mi_ssp_living_arrangement.py
│   ├── mi_ssp_payment_category.py
│   └── mi_ssp_person.py
└── tests/policy/baseline/gov/states/mi/mdhhs/ssp/
    ├── integration.yaml
    ├── mi_ssp.yaml
    ├── mi_ssp_couple_amount.yaml
    ├── mi_ssp_couple_eligible.yaml
    ├── mi_ssp_eligible.yaml
    ├── mi_ssp_individual_amount.yaml
    └── mi_ssp_person.yaml

Also updated:

• policyengine_us/variables/household/income/spm_unit/spm_unit_benefits.py — added mi_ssp to BENEFITS
• policyengine_us/parameters/gov/household/household_state_benefits.yaml — added mi_ssp to 2023 and 2024 sections
• policyengine_us/programs.yaml — updated MI SSP entry with variable: mi_ssp, parameter_prefix: gov.states.mi.mdhhs.ssp, status: complete

Historical Notes

Individual SSP rates have been frozen at the same nominal values since at least 2011 — the SSA 2011 baseline Table 1 values for IL individual ($14), Personal Care ($157.50), Home for the Aged ($179.30), and Institution ($7) match the current 2026 RFT 248 schedule exactly. Couple rates for Domiciliary Care, Personal Care, and Home for the Aged adjust annually because they are computed against a moving target that includes the federal couple FBR.

Verification TODO

• Verify payment amounts against RFT 248 (current and historical Wayback snapshots)
• Verify eligibility logic against BEM 660 p.1 (two-track gate by administering agency)
• Verify amounts current as of 2016-2026
• CI passes

Test plan

• 60 tests pass (28 integration + 32 unit across 6 unit-test files)
• CI passes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.55%. Comparing base (8675371) to head (38e2395).
⚠️ Report is 103 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##              main    #8176      +/-   ##
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- Coverage   100.00%   95.55%   -4.45%     
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  Files            3        9       +6     
  Lines           39      135      +96     
  Branches         0        2       +2     
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+ Hits            39      129      +90     
- Misses           0        6       +6     

Flag	Coverage Δ
unittests	95.55% <100.00%> (-4.45%)	⬇️

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