BUTTERFLY

EEOI above 100,000 is withheld. Those values come from returns where reported transport work is near zero, which makes the ratio meaningless rather than extreme. Median across the dataset is around 12.

Emission categories overlap. In the MRV return, emissions at berth are also counted inside the voyage legs, so the categories do not sum to the total. They are shown side by side rather than stacked for that reason.

Distance is derived, intensity is reported. The MRV return publishes CO₂ per nautical mile but not the distance itself, which is null in all 106,564 rows of the source. The distance column is therefore filled from the ranking step, which reconstructs it, and is blank for years where a vessel was not ranked. That is why a row can show an intensity without a distance.

Percentile is within type and year. It is the vessel's position among qualifying ships of the same type that year, where lower is more efficient. A blank means the vessel did not qualify for ranking that year.

Sister ships share a builder, a type and a build year within two years of this vessel. That holds hull and machinery roughly constant and leaves operation as the variable, which is why they are listed before nearest-by-tonnage.

Methane and nitrous oxide start in 2024. They were not reported before that period, so earlier years cannot be compared against them.

Technical efficiency is a design figure fixed at construction. A vessel can hold a good index and still emit heavily by sailing fast, waiting at anchor or carrying little.

Inspection records cover United States waters only. An empty record is not evidence of a clean history elsewhere.

Empty means unreported, never zero. Nothing here is modelled, estimated or interpolated. See the methodology.

Something wrong on this page? See corrections. We do not hold the source registers and cannot amend them, but we will fix anything we have got wrong in reproducing them.