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title: "Free Trade and the Formation of Environmental Policy: Evidence from US Legislative Votes"
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[Jevan Cherniwchan; Nouri Najjar (2025)](https://doi.org/10.1257/pol.20230733). *American Economic Journal: Economic Policy*.

**Under development — community extension.** This is a provisional source-design assessment, not a new successful replication or a final eligibility ruling.

[Extension index](development.html) · [Provisional eligibility log](development.html#eligibility-log) · [Assessment JSON](aeraej-128.json) · [QMD](aeraej-128.qmd) · [Reproduction code](collection-code.zip)

## Source design and template applicability

TreatImp and TreatExp are continuous import/export tariff-reduction exposures interacted with the NAFTA period. The design is continuous-treatment DiD, outside this binary-treatment template rather than invalid DiD.

No DiD estimates, uncertainty intervals or homogeneity-test decision were computed in this tranche. No point is added to the calibration plots. This is not a zero effect or a failed statistical test.

## Recorded treatment-column measurement

**405 distinct nonmissing values** in `TreatImp`.

Observed support in the indicated source frame; missing values excluded. N=52,312; missing=0. Frame: selected_source_data. Source: /Volumes/LAL_BAK/did-cardinality-work/packages/Cherniwchan_Najjar_AEJ-Policy_2025_201822/processed/analysis/nafta_house_1990_2001_clean.dta.

These are the existing data-measured counts, not counts inferred from design labels. A binary instrument, group indicator or interaction component need not be the treatment of interest; the source-design assessment above takes precedence for template applicability.

## Replication status

**This tranche:** unsupported design; source code/documentation inspected, no estimator run.

**Supplied library:** verified; verification: verified; preparation: runs_with_shim. These are the library’s labels, not new verification claims. Missing data and unsupported designs are separate issues.

## Evidence and provenance

The following files in the supplied library were inspected. Their SHA-256 digests are recorded in the downloadable assessment JSON. Source archives and microdata are not redistributed.

- `AEJ-Policy/Cherniwchan_Najjar_AEJ-Policy_2025_201822/R/128_cherniwchan_najjar_figure.R` (84 lines)
- `AEJ-Policy/Cherniwchan_Najjar_AEJ-Policy_2025_201822/R/128_cherniwchan_najjar_replicate.R` (271 lines)
- `AEJ-Policy/Cherniwchan_Najjar_AEJ-Policy_2025_201822/verdict.md` (71 lines)
- `AEJ-Policy/Cherniwchan_Najjar_AEJ-Policy_2025_201822/aeraej-128.md` (240 lines)