ESG scores don’t always agree. That’s okay.

Your company can have a strong score with one ESG rater and a mediocre one with another, and neither score may be wrong. How is that possible? The raters aren’t disagreeing about your company. They’re just asking different questions, built on different assumptions about what matters.

Four raters, four different questions

MSCI, Sustainalytics, S&P Global, and ISS ESG are the four primary ESG ratings providers most of our clients engage with. A common mistake is to treat these raters as interchangeable competitors measuring the same thing. They’re not.

• MSCI compares a company’s ESG risk management to its industry peers and assigns a letter grade for the result, running from AAA down to CCC. A company doesn’t need to be flawless to score well, but it does need to handle its risks better than peers.
• Sustainalytics flips the question. Instead of asking how well risk is managed, it asks how much risk is unmanaged, and scores that on a numeric scale where lower is better.
• S&P Global takes a different approach with its Corporate Sustainability Assessment (CSA). Companies fill out a detailed questionnaire and submit it directly. That makes S&P the only rater of the four where the company’s own submission is the primary input rather than public disclosure. S&P produces two distinct scores: the CSA Score, built from the questionnaire alone on a 0 to 100 scale, and the S&P Global ESG Score, which is based on a modelling layer using public information. They’re not interchangeable.
• ISS ESG reflects another approach. Rather than ranking companies against each other, it checks whether a company clears a fixed performance bar set for its sector. Clear the bar and earn Prime status, layered on top of a twelve-level letter grade from A+ down to D-.

As each rater measures something different, a strong result from one doesn’t say much about how the others will see the same company.

Why scores diverge

In addition to the underlying differences in the questions being asked by the raters, three structural choices help explain why scores diverge:

• Materiality: MSCI and Sustainalytics only care whether an issue could impact the company financially. S&P Global and ISS ESG go further and ask whether the company’s operations affect the world around it, which pulls a much wider set of topics into scope. A company that has its financial exposure well managed can still come up short with a rater that’s also assessing its broader societal footprint.
• Role of public reporting: S&P Global works from a company-submitted questionnaire. If a company does not submit a questionnaire, the CSA score is calculated based on publicly available information. S&P’s modelled ESG Score and the other three raters all draw from public sources, with varying windows to flag errors: Sustainalytics annually and ISS every two- to-three years. Since May 2026, ISS no longer accepts non-public documents in that process.
• Industry classification: Each rater sorts companies into peer groups, and that grouping determines which issues get assessed and how much weight they carry. Two raters can look at the exact same company’s exact same annual performance and end up comparing it against different peer sets entirely, which alone can move a score without anything about the company changing.

So, what can you do?

Raters may change their ranking methodology. Raters may revise their frameworks. Across all four raters, however, one input is constant: the information a company has made public. A company’s sustainability reporting is the one thing that doesn’t shift. Strong, well-structured sustainability reporting is the foundation every rater builds from, and investing in it is central to a robust rater/ranker strategy. It won’t guarantee a strong score with any single provider, but it is the input every provider depends on, and the one a company actually controls.