The earliest source of the dispersal of opinions between different ESG rating agencies is most likely the identification of ESG factors.
Identification of ESG factors (A): Different rating agencies may prioritize and identify different ESG factors based on their proprietary methodologies, resulting in variation from the outset. This initial step influences the entire rating process as it determines which aspects of ESG will be assessed.
Determination of weighting and scoring methodologies (B): Although critical, discrepancies in weighting and scoring methodologies come after the identification of ESG factors. These methodologies vary based on the initial set of factors considered important by each agency.
Gathering of a set of data points for the identified ESG indicators (C): This step involves data collection based on the previously identified factors and methodologies. Differences in data sources and quality further contribute to variation, but the foundational divergence starts with factor identification.
References:
CFA ESG Investing Principles
MSCI ESG Ratings Methodology (June 2022)