SBB punctuality statistics

Swiss railways publish the percentage of passengers who make all their connections and arrive less than three minutes late.

How do they calculate this?

I suspect, like ORCATS, it is based on passenger surveys (so if, as a comparison, the 1816 Euston-Brum typically carries 50 passengers connecting at Leighton for Bletchley, as it does roughly, it will be considered that it *always* does). They don't have any means of recording who did what, mostly don't have any form of seat reservations, and they have very few Advance type tickets - almost everyone travels on walk-up fares.

A quick search does not reveal full methodology. SBB notes that it is a digital exercise (so simply punctual or not with no weighting for length of delay). I suspect they simply calculate missed connections given the Taktfahrplan approach and then overlay that on usage (though whether they go into any detail on that I don't know - it could simply be we have x passengers per day and y delayed trains (including connection missed).

Bletchleyite said:

they have very few Advance type tickets - almost everyone travels on walk-up fares.

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I would have thought most people travel on a Swiss pass, but otherwise for intercity travel the website usually offers an "advance" type ticket (i.e. booked train only). I expect tourists staying within a city would use day tickets, which include the Basel and Geneva hotel passes.

Are there any stats which can confirm or refute this?