MASSA 2025 Keelboat Championship

Performance rating asks, for each skipper: holding every other boat fixed, which rating makes my actual race-by-race finishes least surprising? Boats are valued with the keelboat rating rather than the fleet rating: 0.41 × the skipper's fleet rating from the week before the event (unrated skippers start at 0.47); 0.28 × the mean fleet rating of the rated crew aboard; the skipper's own keelboat offset; the school's program effect. Non-finishes (OCS, DNF and similar) are left out of the fitting, as in the rating model.

Percentile places a rating among the 78 ISSA sailors with a keelboat rating who raced the discipline in the last three seasons. Surprise is how many bits more surprising the finishes were at the pre-event rating than at the performance rating. P(this good or better) simulates the event 3,000 times at the pre-event ratings, with the same regatta-form model as the fleet analysis pages, and reports how often the skipper would score this many points or fewer in the races they sailed.

The keelboat offsets are the current ones (the discipline files keep no weekly history), so a skipper's own offset has already seen this event; offsets are shrunk hard, so the effect is a few hundredths at most. Only skippers are rated.