Who keeps coming back

How sure is “the same person”? These exports carry no athlete id, so one person across editions is a normalized name — accent- and case-folded, punctuation stripped, first and last name treated as interchangeable because the organiser swaps them between years. That merges different people who share a name, and the rate is measured rather than assumed: two finishers in the same race are certainly different humans, and 645 such collisions occur among 107,790 named finishes. Applied to every cross-edition pair that predicts roughly 5,676 merges that are two people rather than one. Read the repeat counts as an upper bound.