ESG Ratings and Their Disagreements
ESG Ratings and Their Disagreements
When Standard & Poor's assigns a credit rating of BBB to a bond, every major agency using similar methodology will reach a broadly comparable conclusion. When MSCI assigns an ESG rating of AA to a company, Sustainalytics might call the same company high-risk — the rough equivalent of a junk-bond status. This is not a rounding error. The correlation between major ESG raters' scores for the same companies hovers around 0.5, a level of disagreement that would be scandalous in credit markets and that has profound implications for any investor relying on ESG data.
Why Disagreement Is Structural
The disagreement is not caused by one provider being right and others wrong. It reflects three deep structural differences: what raters choose to measure (scope), how they weight different factors (weights), and what data sources they use to make assessments (measurement approach).
On scope, some providers focus on a company's impact on society and environment — what the EU calls "outside-in" materiality. Others focus on how ESG risks affect the company's own financial performance — "inside-out" materiality. A coal producer looks radically different under these two lenses. Under the first, it is rated poorly because of its contribution to climate change. Under the second, it may receive a moderate rating if it manages its regulatory and physical risks competently.
On weights, a technology company that scores well on carbon emissions (the E) but poorly on data privacy and workforce diversity (S and G) will receive a very different aggregate score depending on whether the rater weights E heavily or treats the three letters equally. Raters rarely disclose their weighting methodologies in detail, making it impossible for investors to fully reverse-engineer a score.
On measurement, some ESG factors can be quantified from public disclosures. Others rely on questionnaires sent to companies — which creates an obvious self-reporting bias, since companies control what they submit and how they frame it. A 2022 study by Berg, Kölbel, and Rigobon, published in the Review of Finance, decomposed ESG rating disagreements and found that divergence in measurement methodology accounted for the largest share of variation, larger even than scope or weighting differences.
What Investors Should Do
No single ESG rating is authoritative. The most sophisticated institutional investors treat ESG scores the way equity analysts treat broker earnings estimates: as useful inputs that require triangulation across multiple sources, not verdicts to be accepted uncritically. Chapters in this section walk through each major provider's methodology, their respective blind spots, and strategies for reconciling conflicting signals in a real investment process.
Articles in this chapter
📄️ How ESG Ratings Work
The mechanics of ESG scoring — what data ESG rating agencies collect, how they weight environmental, social, and governance factors, and how scores are aggregated into a final rating.
📄️ MSCI ESG Ratings
How MSCI's ESG ratings work — the AAA-to-CCC scale, industry-adjusted scoring, key issue weighting, and how MSCI ratings are used in index construction and portfolio analysis.
📄️ Sustainalytics Ratings
How Sustainalytics' ESG Risk Rating methodology works — the risk-based approach, managed vs. unmanaged risk distinction, and how it differs from MSCI's relative performance framework.
📄️ S&P Global ESG
How S&P Global's ESG scoring works — the Corporate Sustainability Assessment questionnaire, industry-specific criteria, the Dow Jones Sustainability Indices, and how the CSA differs from MSCI and Sustainalytics.
📄️ Bloomberg ESG
How Bloomberg's ESG disclosure scores work — the disclosure-based methodology, coverage advantage, and how Bloomberg ESG data integrates with financial data terminals used by professional investors.
📄️ ISS ESG
How ISS ESG quality scores work, the connection between ISS ESG research and ISS proxy advisory services, and what makes ISS distinct among ESG rating providers.
📄️ Refinitiv ESG
How Refinitiv (now LSEG) ESG scores work — the pillar-score architecture, controversy overlay, extensive company coverage, and integration with Eikon and Workspace financial platforms.
📄️ Rating Disagreements
The documented phenomenon of ESG rating divergence — why different ESG raters assign substantially different scores to the same companies, and what it means for investors who rely on ESG ratings.
📄️ Scope Divergence
How differences in what ESG rating agencies measure — the scope of their assessments — cause divergent company ratings, and what specific categories of factors are most contested in scope.
📄️ Weight Divergence
How differences in how much ESG rating agencies weight individual factors — particularly the balance between E, S, and G pillars — contribute to ESG rating divergence and portfolio differences.
📄️ Data Gap Problem
The fundamental data quality challenges in ESG ratings — gaps in coverage, self-reported data without verification, inconsistent methodologies, and what investors need to know about the reliability of ESG metrics.
📄️ Controversy Adjustments
How ESG rating agencies assess and adjust for corporate controversy events — environmental spills, labor violations, governance failures — and the distinction between controversy flags and base ESG scores.
📄️ ESG Rating Coverage
The coverage limitations of major ESG rating agencies — how small-cap companies and emerging market companies are systematically under-covered, and what investors can do about it.
📄️ ESG Washing in Ratings
How companies manipulate or game ESG rating processes — through selective disclosure, questionnaire optimization, and policy adoption without implementation — and what investors can do to identify it.
📄️ AI in ESG Ratings
How machine learning and natural language processing are transforming ESG data collection, analysis, and ratings — the opportunities, limitations, and risks of AI-driven ESG assessment.
📄️ ESG Rating Conflicts of Interest
The business model conflicts inherent in the ESG rating industry — issuer-pays models, consulting revenue, and the independence challenges that may bias ESG assessments.
📄️ ESG Rating Regulation
The emerging regulatory framework for ESG rating agencies — the EU's ESG Rating Regulation, global regulatory developments, and what oversight means for investors who rely on ESG data.
📄️ Using Multiple Raters
Practical strategies for institutional investors using multiple ESG rating providers — how to reconcile conflicting scores, extract the most useful information from each provider, and build a more reliable ESG assessment process.
📄️ Sector-Specific Ratings
How ESG ratings differ by industry sector — the sector-specific factors, weighting approaches, and the key ESG issues that matter most for different industries from energy to technology to healthcare.
📄️ ESG Momentum Scores
How ESG momentum — the change in ESG scores over time — can be used as an investment signal, and the evidence for whether ESG improvement predicts financial performance.
📄️ ESG Rating Transparency
The demand for greater ESG rating methodology transparency — what open-source ESG data advocates argue for, what rating agencies have resisted, and how the transparency landscape is changing.
📄️ Controversies vs. Scores
The analytical distinction between ESG management quality scores and ESG controversy flags — what each measures, how they interact, and why both are necessary for a complete ESG picture.
📄️ ESG Ratings vs. Credit Ratings
The structural differences between ESG ratings and credit ratings — in scope, regulation, methodology, performance validation, and the financial consequences of rating errors.
📄️ Future of ESG Ratings
Where the ESG ratings industry is heading — regulation, consolidation, technology disruption, and the fundamental question of whether a single global ESG standard is desirable or achievable.