ESG Rating Guide — How MSCI, Sustainalytics, S&P, and ISS Rate Companies
MSCI rates Tesla CCC (worst in industry). Sustainalytics rates Tesla Medium Risk. S&P Global gives Tesla a top-quartile ESG score. The same company receives drastically different ratings depending on which agency evaluates it, with an average inter-rater correlation of just 0.54.
ESG rating agencies evaluate companies on environmental, social, and governance factors and assign scores used by asset managers, index providers, and financial institutions. The four largest ESG rating providers — MSCI, Sustainalytics (Morningstar), S&P Global, and ISS ESG — collectively cover over 10,000 companies. The MIT Sloan study "Aggregate Confusion" found that ESG rating correlations average only 0.54 versus 0.99 for credit ratings, meaning these agencies often reach opposite conclusions about the same company. Understanding each methodology is essential for investors relying on ESG data.
Major ESG Rating Agencies and Methodologies
MSCI ESG Ratings (AAA—CCC): Evaluates companies on 31 key ESG issues across 10 categories, weighted by industry materiality. A company's score reflects its exposure to industry-specific ESG risks and its management of those risks relative to peers. Tesla scores CCC because MSCI's methodology heavily weights labor relations, product safety (autopilot), and governance — areas where Tesla lags — while the EV environmental benefit is considered industry-standard. Sustainalytics (Morningstar): Provides ESG Risk Ratings measuring the degree to which a company's economic value is at risk from ESG factors. Scale: Negligible (0-10), Low (10-20), Medium (20-30), High (30-40), Severe (40+). Sustainalytics focuses on unmanaged risk: a company in a carbon-intensive industry can score well if it manages those risks effectively. Tesla scores around 25 (Medium Risk) because it partially manages labor and safety risks. S&P Global CSA Score (0-100): Based on an annual Corporate Sustainability Assessment questionnaire across 61 industry-specific criteria. Scores determine membership in the Dow Jones Sustainability Indices (DJSI). Unlike MSCI and Sustainalytics, S&P's methodology relies heavily on company-submitted data verified by S&P, favoring companies with dedicated sustainability reporting teams. ISS ESG: Rates companies A+ to D- on environmental and social performance plus governance quality, and provides Controversy Screening and SDG Impact Ratings linked to the UN Sustainable Development Goals. Other providers: Refinitiv (LSEG) scores A+ to D- based on 630+ metrics. Bloomberg ESG Disclosure Scores measure what companies actually report, not estimated data. CDP rates A-F specifically on climate change, water security, and deforestation.
FAQs
Why do ESG rating agencies disagree so often?
The average correlation between major ESG rating providers is 0.54, compared to 0.99 for credit ratings. Disagreement stems from several sources: different materiality frameworks (what matters to MSCI may not matter to Sustainalytics), different weighting of E, S, and G pillars (S&P weights governance heavily, MSCI emphasizes environmental issues), different data sources (some use company disclosures, others use media reports and NGO data), and different philosophical approaches (MSCI rates relative industry performance, Sustainalytics measures absolute unmanaged risk). A company like Tesla can be a leader in one framework and a laggard in another because the raters disagree on what matters. Investors should cross-reference at least two providers before making decisions.
How should investors use ESG ratings?
ESG ratings are a starting point, not a definitive assessment. Best practices include: cross-reference at least two rating providers — if MSCI and Sustainalytics both rate a company poorly, the signal is more reliable; focus on material ESG issues specific to each industry (carbon matters for utilities, data privacy for tech, labor practices for retail); monitor controversies rather than just scores — a single major incident like an oil spill or data breach can destroy value regardless of the company's overall rating; and use ratings to identify engagement priorities rather than exclusion triggers. Remember that ESG ratings measure ESG factors, not investment quality — a low-rated company may still be a sound investment if priced appropriately, and a high-rated company may be overvalued.
Do ESG ratings predict performance or risk?
Research shows that ESG ratings have modest predictive power for certain risk events. Companies with poor ESG ratings tend to have higher cost of capital, more regulatory actions, and greater litigation risk. A 2023 study by NYU Stern found that portfolios of high-ESG-rated companies had lower tail risk and smaller drawdowns during market crises. However, ESG ratings are poor predictors of short-term stock returns. The relationship between ESG ratings and financial performance is weak to neutral, with most outperformance concentrated in risk reduction rather than return enhancement. ESG controversy events (negative incidents) are more predictive of stock declines than overall ESG scores. The market reacts most strongly to controversies that were previously undisclosed, suggesting ESG ratings' main value is uncovering information not yet priced in by markets.