I don;t know if anybody understands it...

start off with the whole range of development processes for different ages both here and in Canada U-16 and U-18, the NTDP, B Juniors in Canada, USHL, etc. Then work in the fact that D-1 schools tend to follow two different general approaches - either (1) kids straight out of high school/preps, NTDP (or one year of USHL/BCHL because the staff says they need another year or the schol limit is in play) or (2) somewhat older kids who have eligibility. There's also the idea that kids who are likely 1st or 2d rounders from the gitgo (meaning a lock to go high once they're draft eligible at 18) tend to go to the "name" group of schools unless they're going Major Juniors/NHL instead. So by the time kids sign the letter they're probably in one group or the other. UMD, SCS, and schools like that will generally have older kids and more Canadians (I'll leave out the occasional European, who seem to end up anywhere). It's how a kid from Kelowna BC can end up at Quinnipiac in New Haven. Obviously, this is pretty general and the exception proves the rule.