ESG ratings are scores assigned by independent agencies — such as MSCI, Sustainalytics, and S&P Global — that assess how well a company manages environmental, social, and governance risks. UK investors use them to screen funds, compare companies on sustainability criteria, and identify risks not captured by traditional financial analysis. Ratings vary between providers because each uses different methodologies, so cross-referencing multiple sources is essential for informed decision-making.
ESG Ratings Explained
ESG ratings evaluate companies across three pillars: Environmental (carbon emissions, energy use, waste management), Social (labour standards, data privacy, community impact), and Governance (board diversity, executive pay, anti-corruption policies).
Rating agencies collect data from company disclosures, government databases, media reports, and NGO research. They then apply proprietary models to generate a score — which investors use to assess sustainability risk alongside traditional financial metrics.
£30tn+
Global AUM using ESG ratings in decisions
600+
ESG data providers globally
~60%
Correlation between major rating providers
The Three ESG Pillars: High-Rated vs Low-Rated Company
The radar chart below illustrates how a company with a strong ESG profile (green) compares to one with weak ESG management (amber) across five key dimensions.
Major ESG Rating Providers Compared
Five agencies dominate the ESG ratings landscape. Each uses different scales, coverage, and methodologies — which is why cross-referencing is essential.
| Provider | Rating Scale | Coverage | Approach | Access |
|---|---|---|---|---|
| MSCI | AAA to CCC (7 grades) | 8,500+ companies | Industry-relative, weighted across 35 key ESG issues | Free basic ratings via msci.com |
| Sustainalytics | 0–100 risk score (lower = better) | 16,000+ companies | Absolute ESG risk exposure and management assessment | Available via Morningstar |
| S&P Global | 0–100 ESG score | 10,000+ companies | Based on Corporate Sustainability Assessment (CSA) questionnaires | Free scores via spglobal.com |
| CDP | A to D– (climate focus) | 23,000+ companies | Voluntary climate and environmental disclosure scoring | Free public scores |
| ISS ESG | A+ to D– | 9,000+ companies | Sector-specific norms-based assessment | Institutional only |
Why Do ESG Ratings Differ Between Providers?
A landmark 2022 study by MIT Sloan found only ~60% correlation between major ESG rating providers — compared to over 99% for credit ratings. The same company can receive an "AA" from MSCI and a "High Risk" from Sustainalytics. Here's why:
Different Scope
Providers measure different issues. MSCI focuses on financially material ESG risks; Sustainalytics measures absolute ESG risk exposure; CDP focuses specifically on climate disclosure.
Different Weighting
How much weight each pillar receives varies. One provider might weight carbon emissions at 30% while another weights it at 10% for the same sector.
Different Data Sources
Some rely on company self-disclosure, others use satellite data, news sentiment analysis, or NGO reports. More data doesn't always mean better data.
Rating Divergence in Practice
| Company Type | MSCI | Sustainalytics | S&P Global |
|---|---|---|---|
| Company A (Oil Major) | BBB | High Risk | 42/100 |
| Company B (Tech Giant) | AA | Medium Risk | 71/100 |
| Company C (Utility) | A | Low Risk | 68/100 |
| Company D (Fast Fashion) | B | Severe Risk | 28/100 |
What Each ESG Pillar Measures
The chart below shows how different ESG issues map across the three pillars. Some issues — like data privacy — span multiple pillars.
How UK Investors Should Use ESG Ratings
Cross-Reference Multiple Providers
Never rely on a single rating. Check at least two providers (e.g., MSCI and Sustainalytics) and look for consensus — or investigate when they disagree.
Understand the Methodology
Read the provider's methodology document. Does it measure risk to the company (financial materiality) or the company's impact on the world (double materiality)? The EU now requires double materiality; the UK is moving in that direction.
Check the Underlying Data
Ratings are only as good as the data they're built on. Look for the disclosure score — companies that report more data tend to get higher ratings, which doesn't always mean better ESG performance.
Look Beyond the Headline Score
Dig into pillar-level scores. A company might score 'AA' overall but have a poor environmental score masked by strong governance. Make sure the pillars that matter to you are well rated.
Supplement with Qualitative Research
Ratings don't capture everything. Recent controversies, pending legislation, or supply chain issues may not yet be reflected. An FCA-regulated adviser can provide this qualitative layer for larger portfolios.
Green Flags vs Red Flags When Using ESG Ratings
Green Flags
- • Fund uses multiple ESG data providers, not just one
- • Transparent methodology with published exclusion lists
- • FCA SDR labelling (e.g., "Sustainability Focus" or "Sustainability Impact")
- • Active engagement and voting record disclosed
- • Regular ESG reporting with clear metrics
Red Flags
- • Relies on a single ESG rating without disclosure
- • "ESG integrated" label with no published methodology
- • High ESG score but no exclusion of controversial sectors
- • No engagement policy or proxy voting record
- • Uses ESG ratings as a marketing tool without substance
UK Regulation of ESG Ratings
The UK is moving towards formal regulation of ESG rating providers. Key developments include:
FCA Sustainability Disclosure Requirements (SDR)
Requires fund managers to substantiate sustainability claims. Anti-greenwashing rule in force since May 2024. Fund labelling framework (Sustainability Focus, Improvers, Impact, Mixed Goals) provides clearer guidance.
ESG Ratings Provider Regulation
HM Treasury has consulted on bringing ESG rating providers under FCA oversight. Expected to introduce mandatory transparency requirements for methodologies, conflicts of interest, and data sources.
Transition Plan Taskforce (TPT)
UK companies and financial institutions are expected to publish climate transition plans, improving the quality of data that feeds into ESG ratings.
ISSB Standards Adoption
The UK has endorsed the International Sustainability Standards Board (ISSB) framework, creating a global baseline for sustainability disclosure that will improve ESG data quality.
Common Questions About Ethical Investing
What are ESG ratings?
ESG ratings are scores assigned by independent agencies that assess how well a company manages environmental, social, and governance risks. They help investors compare companies on sustainability criteria and identify potential risks not captured by traditional financial analysis.
Who provides ESG ratings?
The main global providers are MSCI, Sustainalytics (owned by Morningstar), S&P Global, CDP, and ISS ESG. Each uses different methodologies, which is why ratings for the same company can vary significantly between providers.
Why do ESG ratings differ between providers?
ESG ratings diverge because providers use different methodologies, weight ESG factors differently, rely on different data sources, and measure different things — some focus on risk to the company, others on the company's impact on the world. Academic research shows only ~60% correlation between major providers.
Are ESG ratings reliable for investment decisions?
ESG ratings are useful but imperfect tools. They provide a starting point for analysis but should not be the sole basis for investment decisions. Investors should cross-reference multiple providers, check the underlying methodology, and supplement ratings with their own research or adviser expertise.
Does the FCA regulate ESG ratings in the UK?
Not yet directly, but the FCA has signalled plans to bring ESG rating providers under regulatory oversight. The UK's Sustainability Disclosure Requirements (SDR) already require fund managers to substantiate any sustainability claims, and the FCA's 2024 consultation on ESG ratings regulation is expected to result in a formal framework.
Important Information
This article is for information only and does not constitute financial advice. ESG ratings are provided by independent third parties and their methodologies may change. The value of investments can fall as well as rise and you may get back less than you invest. Past performance is not a reliable indicator of future results. Lifemap Financial Planning Ltd is authorised and regulated by the Financial Conduct Authority (FCA No. 813341).