You're mostly right. I used to work in Cable TV, We would see up to 80% for very good coaxial cablingTwisted pair cabling is a bit lower.
en.wikipedia.org/wiki/Wave_propagation_speed
(en.wikipedia.org/wiki/Wave_propagation_speed
PedroHin Come along & ride on a Flantastic Voyage,
Fri 11 Sep 2009, 1:55,
archived)