ESG Reliability Post‐Paris Agreement: Evidence From S&P 500 Firms

ABSTRACT This research investigates whether the 2015 Paris Agreement has changed environmental, social, and governance (ESG) performance scores. We compiled a balanced panel of 392 S&P 500 companies from 2010 to 2025 using Refinitiv data. The final dataset contained 6272 observations on the 10 ESG scores at the most detailed level possible. Based on stakeholder theory, interrupted time series analysis (ITSA) was applied to determine whether the intercorrelations among the ESG variables decreased post‐Paris. Moreover, in accordance with legitimacy theory, the reported ESG measures were examined using Benford's law. It was found that the uniformity of the last digits improved over time. Three robustness checks were carried out: (a) an out‐of‐sample ITSA with 293 STOXX‐listed companies, (b) a quadratic ITSA, and (c) placebo tests with different breakpoints. The evidence indicates (1) the downward trend became stronger in the period after the Paris Agreement and (2) the differentiation among ESG scores accelerated in a nonlinear manner. We conclude the reliability of ESG performance scores has increased over time, providing a more trustworthy foundation for stakeholders' decision‐making.