# Washington gasoline price premium and the Climate Commitment Act, 2015-2026

FactHub-curated research dataset. Not an official publication of EIA, Ecology, or the State of Washington.

## What this is
Weekly EIA retail regular gasoline prices for Washington and comparison regions (2015-01-05 to 2026-10-05), Ecology quarterly allowance auction prices (2023Q1-2026Q3), and Washington taxed fuel volumes, with saved analyses estimating the Washington-specific price change since the Climate Commitment Act began on 2023-01-01.

## Method
1. Inflation-adjust weekly prices to January 2024 dollars (CPI-U; October 2025 CPI interpolated because BLS did not publish it).
2. Normalize Washington prices to a constant 49.4-cent state gas tax.
3. For each comparison region, compute the weekly Washington-minus-comparison gap.
4. Effect for a period = mean gap in the period minus mean gap in 2015-2022 (Newey-West standard errors, 12 lags).
5. Carbon cost per gallon = auction settlement price x EPA emission factor (gasoline E10: 8.78 x 0.90 kg CO2/gal; diesel 10.21).
6. Cost = per-gallon cost x taxed gallons (TRFC).

This mirrors the method of Greene Economics for Ecology (Pub. 26-14-043) and extends it through 2026.

## Reproduce
Download the sources listed in source-manifest.json into one directory, then run:
node did.js <raw> <out>; node passthrough.js <out>/did_results.json <raw>/CPIAUCSL.csv; node cost.js <out>/did_results.json <raw>/CPIAUCSL.csv <out>/cost.json; node build_release.js <out> <raw> <scripts> <release>
Node.js 20, no packages.