"Report and ratings methodology, scope and coverage, however, vary greatly among providers. Many providers encourage input and engagement with their subject companies to improve or sometimes correct data. Third party ESG report and ratings providers include: (i) Bloomberg ESG Data Service; (ii) Corporate Knights Global 100; (iii) DowJones Sustainability Index (DJSI); (iv) MSCI ESG Research; (v) RepRisk; (vi) Sustainalytics Company ESG Reports; and (vii) Thomson Reuters ESG Research Data. This memorandum provides an overview and analysis of these providers."

[COMMENTARY] Davis Polk provides a good overview of ESG raters and their methodologies. The review also covers ESG ETFs and portfolios.
ESG Reports and Ratings: What They Are, Why They Matter, by Davis Polk, July 12, 2017, 7 Davis Polk & Wardwell LLP, USA.