Update ACA take-up time series

Author: daphnehanse11

changelog.d/changed/620.md

@@ -0,0 +1 @@
+Update the ACA take-up parameter with a KFF-based time series for 2023 through 2026.

policyengine_us_data/parameters/take_up/aca.yaml

@@ -5,6 +5,14 @@ metadata:
   period: year
   reference:
     - title: KFF "A Closer Look at the Remaining Uninsured Population Eligible for Medicaid and CHIP"
-      href: https://www.kff.org/uninsured/issue-brief/a-closer-look-at-the-remaining-uninsured-population-eligible-for-medicaid-and-chip/#:~:text=the%20uninsured%20rate%20dropped%20to,States%20began%20the
+      href: https://www.kff.org/affordable-care-act/state-indicator/distribution-of-eligibility-for-aca-coverage-among-the-remaining-uninsured/
+    - title: KFF State Health Facts, Open Enrollment Marketplace Plan Selections, 2014-2026
+      href: https://www.kff.org/affordable-care-act/state-indicator/open-enrollment-marketplace-plan-selections/
 values:
   2018-01-01: 0.672
+  # Marketplace plan selections / (plan selections + 2023 tax-credit-eligible uninsured).
+  # KFF reports 8,163,000 uninsured people eligible for Marketplace tax credits in 2023.
+  2023-01-01: 0.667088
+  2024-01-01: 0.724308
+  2025-01-01: 0.748697
+  2026-01-01: 0.739150

tests/unit/test_stochastic_variables.py

@@ -37,6 +37,13 @@ def test_aca_rate_loads(self):
         rate = load_take_up_rate("aca", 2022)
         assert 0 < rate <= 1
 
+    def test_aca_rate_uses_marketplace_enrollment_time_series(self):
+        assert load_take_up_rate("aca", 2022) == 0.672
+        assert np.isclose(load_take_up_rate("aca", 2023), 0.667088)
+        assert np.isclose(load_take_up_rate("aca", 2024), 0.724308)
+        assert np.isclose(load_take_up_rate("aca", 2025), 0.748697)
+        assert np.isclose(load_take_up_rate("aca", 2026), 0.739150)
+
     def test_head_start_rate_loads(self):
         rate = load_take_up_rate("head_start", 2022)
         assert 0 < rate <= 1