Sounds like an interesting research project for someone with a whole lot of free time.
Last year, I rode a combination of the Southern Tier/Grand Canyon Connector/Western Express.
On the ST I met 13 touring cyclists. Some (7) were riding the whole route and the rest were riding only part of it and some were riding parts of it in subsequent years ie. I met a couple who were riding the Del Rio to St Augustine section, having ridden from San Diego to Del Rio in one or two previous stages.
On the GCC, I met 4 touring cyclists, 2 of whom didn't have ACA maps, and were simply doing their own tour. I met those 2 cyclists at the North Rim of the Grand canyon. I did see another 2 touring cyclists riding into the North Rim, but never got to meet them.
On the WE, I met 5 touring cyclists. I kept getting told that there were 2 touring cyclists a day's ride ahead of me, but I never caught up with them.
All the cyclists I met, bar 2 on the ST, were coming the other way to me, which is obviously the reason I got to meet them.
In 1991, I cycled the Northern Tier. On that ride, I either met or saw 69 touring cyclists. 60 were coming in the opposite direction and 9 were riding the same way as me. Of course, I never got the full stories of all 69 riders, however 69 over an 11 week period was surprisingly high I felt.
As I said, it would make for an interesting project, but it would never be 100% accurate.