Aussiestatman, on an American website, you're asking why I would contextualize an Aussie 15 year old's mile time by reference to the best ever American sophomores? That is an age group standard that can allow us to judge how good a prospect this kid is, since millions of Americans have run middle distance in formal track programs as sophomores. Since he compares favorably to the top five American sophomores of all time, we can say reasonably that he is a great prospect. And, to respond to runninghelper, because this kid is turning 16 in June, he would be a sophomore in this country and thus should be compared not with 15 year olds--for age group records, he'd count as 16, because he will turn 16 this year--but with those turning 16, and the vast majority of American sophomores turn 16 prior to September.