but why is the relevant percentage the percentage who could do it right now?
isn't it a better measure of the level of accomplishment involved to ask how many people could do it with some reasonable amount of preparation (say, 6 months of training)? think about some silly skill-based record, like bouncing a ball so it hits a certain spot (perhaps a bad example, it's the best i could do off the top of my head). if some kid practices for months and is able to hit that spot every time, is it fair to say that the proper measurement of the impressiveness of the feat is to compare it with the number of people world-wide who could do it at this moment? or does it make more sense to consider how difficult it is to acquire the skill necessary to accomplish the feat? that is, to consider both preparation and age.
in other words, i think we can all agree that with perhaps a handful of exceptions, nobody in the world younger than about 8 years old or older than 60 years old can run a 5 minute mile. but some portion of this group will be able to in the future and some portion was able to and/or did at some point in the past. shouldn't that be taken into account?
so when you are looking around your office at 55 year olds who are overweight, think of them not as fat 55 year olds, but rather as fit 21 year olds. same goes for these high school anecdotes. think not of your 100 person track team, think of those 100 people at their prime mile-running age, which for most, if not all, of them is in the future.
you wouldn't say that a world's best (of the year) 1500 run on january 1st is the best ever 1500, so why would you only consider the ability to run a 5:00 mile today when considering how impressive the accomplishment of breaking 5 minutes for the mile is?