Racing doesn't work that way. There will never be an average that means anything. You could have 2 Cat5 groups do the same course, same conditions on different days and the numbers could be anywhere depending on a bunch of things.

I've been in races that the "average" speed was down around 20-21 that were brutally hard.I've also done races where the "average" was around 26-27 and I spent the day in zone 2 just spinning along.