Thanks for looking this up, it's really interesting. Stats can say many things and I have two thoughts: first, four minutes is an arbitrary line. At current levels, there is a lot of room under four minutes with the WR being 3:43. I suspect athletes like ElG, Scott and many others with PRs under 3:50 could run sub 4:00 in hard training sessions. On the other hand, if your absolute lower limit is 3:59 or 3:58, you'd be far more likely to break four minutes only once or twice in a near perfect race. Second, with the category being American high schoolers who have run sub four, we are dealing with a very small sample. I don't have the research skills to look it up, but I'd guess that generally, guys who have broken four minutes at age 18 have many more sub-4:00 miles, on average, then guys who first break the barrier at age 28 in the prime of their career. Thanks.