Marshall Group

How the Mycelium Score is calculated

The Mycelium Score is out of 10. Up to 6.5 points reflect carbon intensity vs peers in the same NACE section (emissions normalised against revenue, log-scaled between the 5th and 95th percentile of each company's latest reporting year in that section; a section needs at least 5 companies to be benchmarked). The band above 6.5 is earned through verified data quality on a claimed profile: declaring every reporting category yourself (up to 2.0), preparation by a carbon accountant (2.0) and independently audited figures (2.0). The total is multiplied by the transparency score and capped at 10. A disclosure with an implausibly large figure (Scope 1 or 2 over 300 million tonnes, a Scope 3 figure over 2 billion tonnes or a total over 2.5 billion tonnes) is not scored until it has been checked.

A higher score means lower carbon intensity than sector peers, backed by data that's third-party verified, claimed by the company, and fully disclosed. Without a revenue figure to measure carbon intensity, or an industry classification to compare it within, a company has no score.

How the Transparency Score is calculated

The Transparency Score is the share of a company's estimated footprint that it reported itself, graded from A (very high) down to F (very low). Where a category is missing, Mycelium models what it would hold for a company of that size and industry and counts it as undisclosed, so an unreported category where the bulk of emissions sit hurts far more than a minor one. Unreported downstream categories (9 to 15) count at a quarter of their modelled size in this share; the carbon intensity behind the score still counts them in full. A Scope 3 total filed without a category breakdown earns very little credit for the part left unattributed, because it does not show which categories are inside it: a company can count business travel, leave purchased goods out entirely, and the total looks the same. Without a revenue figure the footprint cannot be modelled, so the company has no Transparency Score.

Marshall Group has disclosed the categories that carry most of its estimated footprint, so there's no single bucket dragging the transparency score down. The breakdown above shows which figures are reported and which are modelled.

Read the full scoring methodologyOur white paper covers exactly how the Mycelium Score and Transparency Score are calculated, including the normalisation process and what earns a 10/10.Download the white paper (PDF)