Share one HHS SMI helper for LIHEAP income limits

changelog.d/liheap-smi-helper.changed.md

@@ -0,0 +1 @@
+Share one HHS state median income helper for the LIHEAP income limits in Mississippi, Maryland and New Jersey, and reuse the SMI household-size factor in Colorado CCAP.

policyengine_us/variables/gov/hhs/hhs_smi.py

@@ -1,17 +1,37 @@
 from policyengine_us.model_api import *
 
 
-def smi(unit_size, state, period, parameters):
+def smi_size_factor(unit_size, period, parameters):
+    """Return the 45 CFR 96.85(b) share of the four-person SMI for a size."""
     p = parameters(period).gov.hhs.smi
     size_threshold = p.additional_person_threshold
     capped_size = clip(unit_size - 1, 0, size_threshold - 1)
     extra_persons = max_(unit_size - size_threshold, 0)
-    size_adjustment = (
+    return (
         p.household_size_adjustment.first_person
         + p.household_size_adjustment.second_to_sixth_person * capped_size
         + p.household_size_adjustment.additional_person * extra_persons
     )
-    return p.amount[state] * size_adjustment
+
+
+def smi(unit_size, state, period, parameters):
+    p = parameters(period).gov.hhs.smi
+    return p.amount[state] * smi_size_factor(unit_size, period, parameters)
+
+
+def liheap_smi_limit(unit_size, state, rate, period, parameters):
+    """Return the LIHEAP limit at a rate of the size-adjusted SMI.
+
+    HHS multiplies the rate times the four-person SMI by the size factor
+    (LIHEAP IM 2025-02, Attachment 4). Flooring the four-person amount, then
+    the size-adjusted amount, reproduces the published tables; HHS does not
+    state a rounding order. Pass an earlier date as the period to use a prior
+    year's SMI.
+    """
+    four_person_smi = parameters(period).gov.hhs.smi.amount[state]
+    four_person_limit = np.floor(four_person_smi * rate)
+    size_factor = smi_size_factor(unit_size, period, parameters)
+    return np.floor(four_person_limit * size_factor)
 
 
 class hhs_smi(Variable):

policyengine_us/variables/gov/states/co/ccap/co_ccap_smi.py

@@ -1,4 +1,5 @@
 from policyengine_us.model_api import *
+from policyengine_us.variables.gov.hhs.hhs_smi import smi
 
 
 class co_ccap_smi(Variable):
@@ -18,16 +19,4 @@ def formula(spm_unit, period, parameters):
             instant_str = f"{year}-10-01"
         else:
             instant_str = f"{year - 1}-10-01"
-        four_person_smi = parameters(instant_str).gov.hhs.smi.amount[state_code]
-        adjustment_mapping = parameters(
-            instant_str
-        ).gov.hhs.smi.household_size_adjustment
-        first_person_rate = adjustment_mapping.first_person
-        second_to_sixth_additional_rate = adjustment_mapping.second_to_sixth_person
-        seven_or_more_additional_rate = adjustment_mapping.additional_person
-        size_adjustment = (
-            first_person_rate
-            + second_to_sixth_additional_rate * (min_(size, 6) - 1)
-            + seven_or_more_additional_rate * max_(size - 6, 0)
-        )
-        return four_person_smi * size_adjustment / MONTHS_IN_YEAR
+        return smi(size, state_code, instant_str, parameters) / MONTHS_IN_YEAR

policyengine_us/variables/gov/states/md/dhs/meap/eligibility/md_meap_income_limit.py

@@ -1,5 +1,5 @@
 from policyengine_us.model_api import *
-from policyengine_us.variables.gov.hhs.hhs_smi import smi
+from policyengine_us.variables.gov.hhs.hhs_smi import liheap_smi_limit
 
 
 class md_meap_income_limit(Variable):
@@ -28,10 +28,6 @@ def formula(spm_unit, period, parameters):
         p = parameters(period).gov.states.md.dhs.meap.eligibility
         size = max_(spm_unit("md_meap_household_size", period), 1)
         state = spm_unit.household("state_code_str", period)
-        base = parameters(period).gov.hhs.smi.amount[state]
-        factor = smi(size, state, period, parameters) / base
-        # ACF LIHEAP IM 2025-02 Attachment 4 (page 5) floors 60% of the
-        # four-person SMI, then floors each size's share of it.
-        smi_limit = np.floor(factor * np.floor(base * p.smi_rate))
+        smi_limit = liheap_smi_limit(size, state, p.smi_rate, period, parameters)
         poverty_limit = spm_unit("md_meap_fpg", period) * p.fpg_rate
         return where(size >= p.smi_min_size, smi_limit, poverty_limit)

policyengine_us/variables/gov/states/ms/mdhs/liheap/ms_liheap_income_limit.py

@@ -1,4 +1,5 @@
 from policyengine_us.model_api import *
+from policyengine_us.variables.gov.hhs.hhs_smi import liheap_smi_limit
 
 
 class ms_liheap_income_limit(Variable):
@@ -18,16 +19,6 @@ def formula(spm_unit, period, parameters):
         p = parameters(period).gov.states.ms.mdhs.liheap
         size = spm_unit("ms_liheap_household_size", period)
         state = spm_unit.household("state_code_str", period)
-        federal = parameters(period).gov.hhs.smi
-        # The published FY2026 limits truncate the four-person 60% SMI amount
-        # first, then the household-adjusted amount. This reproduces all 20 rows;
-        # it is a reconciled numerical pattern, not an explicit rounding rule.
-        four_person_limit = np.floor(federal.amount[state] * p.income_limit)
-        adjustment = federal.household_size_adjustment
-        threshold = federal.additional_person_threshold
-        size_share = (
-            adjustment.first_person
-            + adjustment.second_to_sixth_person * clip(size - 1, 0, threshold - 1)
-            + adjustment.additional_person * max_(size - threshold, 0)
-        )
-        return where(size > 0, np.floor(four_person_limit * size_share), 0)
+        # The HHS floor order reproduces all 20 published FY2026 rows.
+        limit = liheap_smi_limit(size, state, p.income_limit, period, parameters)
+        return where(size > 0, limit, 0)

policyengine_us/variables/gov/states/nj/dca/liheap/eligibility/nj_liheap_income_limit.py

@@ -1,5 +1,5 @@
 from policyengine_us.model_api import *
-from policyengine_us.variables.gov.hhs.hhs_smi import smi
+from policyengine_us.variables.gov.hhs.hhs_smi import liheap_smi_limit
 
 
 class nj_liheap_income_limit(Variable):
@@ -32,15 +32,11 @@ def formula(spm_unit, period, parameters):
         p = parameters(period).gov.states.nj.dca.liheap.eligibility
         size = max_(spm_unit("nj_liheap_household_size", period), 1)
         state = spm_unit.household("state_code_str", period)
-        smi_parameters = parameters(period).gov.hhs.smi
-        base = smi_parameters.amount[state]
 
         def monthly_limit(table_size):
-            factor = smi(table_size, state, period, parameters) / base
-            # ACF LIHEAP IM 2025-02 Attachment 4 (page 2) floors 60% of the
-            # four-person SMI, then floors each size's share of it; the fact
-            # sheet's monthly column rounds that half up (not half to even).
-            annual = np.floor(factor * np.floor(base * p.smi_rate))
+            annual = liheap_smi_limit(table_size, state, p.smi_rate, period, parameters)
+            # The fact sheet's monthly column rounds the HHS annual limit half
+            # up (not half to even).
             return np.floor(annual / MONTHS_IN_YEAR + 0.5)
 
         monthly = monthly_limit(min_(size, p.max_table_size))