Books versus Atmosphere: Corporate Boundary Change and the Measurement of U.S. Electric Utility Decarbonisation, 2018–2023

Abstract

Most of the largest U.S. electric power parents announced net-zero or deep carbon-reduction targets between 2018 and 2023, and reported emissions fell over the same period. Corporate emission reductions and atmospheric abatement are not equivalent, because the corporate boundary moves when ownership shares change hands. A facility-level panel from the U.S. Environmental Protection Agency Greenhouse Gas Reporting Program for 2018–2023 allocates emissions to parent companies by reported ownership share under a label-level crosswalk, and decomposes each parent’s change into an operating change on shares held in both years, shares that departed, and shares newly held. Across the 43 parents emitting at least 10 Mt CO₂e in either year, headline changes range from −100% to +22%, and 36 parents reduced. One reduction reflects a change in reported parent attribution rather than a transaction; excluding it, gross reduction across the remaining 35 reducing parents is 312.6 Mt CO₂e, of which departed shares accounted for 59.2 Mt of 2023 emissions, or 19.0%. Including it gives 325.0 Mt, 69.4 Mt and 21.4%. The effect is concentrated: four of the 35 exceed a 50% transfer ratio while seventeen show none. Disclosure rules should require ownership-driven emission changes to be reported separately from operational ones.