Re: Substantial majority
"How about only being able to advertise the speed which say 90% of customers will experience for 90% of the time "
Your line speed is your line speed. It doesn't vary.
Your 90% of the time issue is about throughput and that's down to how much contention you're paying for. Less contention = higher cost. How do you define 90% of the time? Actual usage time will vary from user to user and the throughput will be a function of how many other people are sharing your bandwidth and what they're doing.