@771c7916 I guess overbooking is much more likely in places where there's a lot of connections per area. If you have to provide a lot of connections in a street full of appartments then either you need expensive routers that can provide multi-gigabits bandwidth on a single fiber, or lay a lot of fibers. Both are expensive options which makes connections expensive. overbooking seems a lot more efficient then, especially if usage is mixed commercial/residential. 

 @49a8afa7 yes, not at all dense by us - it's all flat houses spaced out in a suburban area. The max speed is 500 Mbps for the area, and I think most users are really on 40 or 100 Mbps only. But like I say, my router speed test certainly shows the line is performing at full speed outside my home. If it was a contention ratio issue, I'd expect that figure to be lower and much more inconsistent.