Introduction:*

The explosion in ESG research has led to a strong reliance on ESG rating pro viders. We document widespread changes to the historical ratings of a key rating provider, Refinitiv ESG (formerly ASSET4). Depending on whether the original or rewritten data are used, ESG-based classifications of firms into ESG quantiles and tests that relate ESG scores to returns change. While there is a positive link between ESG scores and firms’ stock market performance in the rewritten data, we fail to observe such a relationship in the initial data. The ESG data rewriting is an ongoing rather than a one-off phenomenon.

*Co-authored with F. Berg (MIT) and K. Fabisik (Frankfurt School of Finance and Management and ECGI)