qualified_passenger_vehicle_loan_interest is never imputed — OBBBA auto-loan deduction is structurally $0

Summary

The dataset imputes total auto-loan interest but not the qualifying subset the OBBBA deduction keys on, so the auto-loan-interest provision is structurally zero in reform validation — unvalidatable, and any analysis touching the provision silently shows no effect.

Evidence

On the released populace_us_2024.h5 (…f0af251…20260620), household table:

But PE-US's auto_loan_interest_deduction is computed from qualified_passenger_vehicle_loan_interest — interest on loans meeting the OBBBA vehicle/loan requirements (new vehicles, US final assembly, 2025–2028; IRS Pub 6126). That variable is a pure input with no formula, and populace does not impute it, so it defaults to $0 for every household → the deduction is $0 by construction.

Reform-validation result: populace $0.0 vs JCT −$5.4B (FY2026) / −$8.1B (FY2027) (JCX-35-25 Ch.2 line 3, effective interest incurred after 12/31/24).

Suggested fix

Impute qualified_passenger_vehicle_loan_interest as a share of the existing auto_loan_interest — e.g. apportion by the share of loans that are for qualifying new, US-assembled vehicles (new-vehicle financing shares are published; US-final-assembly share can be approximated from sales data), or calibrate the qualifying share so the simulated deduction is benchmarkable.

Found via the reform-validation page in PolicyEngine/calibration-diagnostics; sibling of #225 (SSN/citizenship imputation gap).

Start with the reform-validation page and the released populace_us_2024.h5 household variables, especially auto_loan_interest and qualified_passenger_vehicle_loan_interest. Trace how the latter feeds auto_loan_interest_deduction, then use the OBBBA requirements, published new-vehicle financing shares, US final-assembly sales data, or calibration targets to define and validate the imputation against the JCT FY2026 and FY2027 benchmarks.