There have been 21 males and 2 females who have completed 20 or more classic Birkies since 1999. The individual results of the male racers are provided in the graph above along with a summary curve.
A longitudinal approach gets a little sketchy with low numbers of racers, so females were dropped from the graph. The number of males is probably adequate for graphical presentation. As with the 20+ year freestyle analysis, male skiers have a prolonged period of stable performance until they are nearly 60 years old, and this was shown in the cross-sectional analysis as well.
Note: Finish times are standardized to a 55k classical race or a 50k freestyle race.