How many voice channels can a single UTP cable carry?

I am doing a presentation for Optical Fibers, and I wanted to showcase the difference in voice channels that each can carry. Firstly, I thought to compare it against the 762 channels first tested in Chicago, but couldn't find anything, so I decided to compare more recent data, although still I came up with nothing. The only clue I have is from a book called "Data Communications: An Introduction to Concepts and Design", which states that the half-inch diameter fiber optic cable carries 15.000 channels (presumably around the times of the Chicago testing), more than seven times the channels a twisted wire-pair carries.
If anyone could answer me, either about the channels during the period of testing, or the current UTP cables, it would be greatly appreciated.