Expand JCT target coverage: JCX-45-25 vintage + RCC-relevant lines (CTC/EITC/CDCC/ALD/OBBBA)

Context

We just finished a scoring validation pass on the 9 refundable-credit-conversion repeal toggles (CTC, EITC, CDCC, standard deduction, itemized, ALD, OBBBA bundle, §199A QBI, head-of-household) against JCT JCX-45-25 and JCX-22-25R. We pulled the populace-us release on Hugging Face (populace-us-2024-f0d2ef6-09292aa0d5db-20260617T032307Z) hoping the target surface could anchor the validation, and ran into two issues worth raising here.

What the target surface covers today

Issue 1 — JCT family uses JCX-48-24, not JCX-45-25

The latest JCT tax-expenditure document is JCX-45-25 (Estimates of Federal Tax Expenditures for Fiscal Years 2025-2029, Dec 2025). The repo's jct family still anchors on the earlier JCX-48-24 at CY2024. The two disagree on every line (different fiscal-year window, post-OBBBA mortgage interest is $53.0B in JCX-45-25 vs $24.8B in JCX-48-24, etc.), and downstream consumers validating against the newer vintage end up double-checking which JCT cell they're matching against.

Proposal: load JCX-45-25 alongside JCX-48-24 (or replace it). FY2026 and FY2027 are the cells we need most for OBBBA-era scoring.

Issue 2 — Five-line jct family is too narrow for tax-expenditure validation

Today the JCT family covers SALT, mortgage interest, charitable, medical, and §199A. For RCC validation we hit gaps on:

Proposal: add JCT tax-expenditure lines for at least the refundable credits (CTC/ACTC, EITC, CDCC) and above-the-line deductions JCT does score (traditional IRA, SE-pension, SE-health, HSA, SLID, educator). For OBBBA, the natural source is JCX-22-25R (Estimated Revenue Effects of the OBBBA) — that's the document we used in PR #48.

Issue 3 — Residuals on the 5 JCT lines we do have are eye-catching

(Aggregate fit is 94.65% within 10%, so these tax-expenditure lines are sitting in the long tail.) Interestingly the toggle revenue impact in PE-US comes out reasonably close to JCX-45-25 on these (e.g. QBI -19%), suggesting microsim formulas are compensating for the under-represented base. Worth a separate look at whether these targets are getting enough calibration pressure.

What this would enable

With JCX-45-25 + CTC/EITC/CDCC/ALD/OBBBA lines loaded, the surface becomes a one-stop validation source for the RCC project (and any subsequent reform-modeling work scoring against JCT). Today we hand-transcribe ~25 JCT cells per validation run; tomorrow we could join PE-US output against a single JSON.

Cross-reference

• PolicyEngine/refundable-credit-conversion#48 — the validation effort that surfaced these gaps
• scripts/scoring_validation/comparison.csv (in that PR) — column populace_calibration_residual now reports the 5 existing JCT residuals plus SOI residuals for CTC/EITC/QBI
• scripts/scoring_validation/pull_calibration_residuals.py — pulls the residuals from this surface

Happy to write up the JCX-45-25 table parsing if it helps.

Start with scripts/scoring_validation/pull_calibration_residuals.py and scripts/scoring_validation/comparison.csv, then review the existing jct target surface against PR #48 and the JCX documents named here. Add JCX-45-25 coverage and the proposed CTC/ACTC, EITC, CDCC, above-the-line, and OBBBA lines, preserving or intentionally replacing JCX-48-24. Done means the targets are available in one JSON surface and residual comparisons no longer require hand-transcription.