Interesting graph, Mr Silver. I appreciate the use of visual aids.
When I was an undergraduate, I heard a lecture presented by visiting artist Steve "Thunder" McGuire, an art professor at the University of Iowa. He cycles within and outside the US and presents a captivating monologue of his epic adventures. He travels with a 2 seater recumbent built to invite people to join him in his journeys. In the latest issue of Outside magazine, he competed in the Great Divide Race, a grueling journey that starts in Montana and ends in Mexico. His age? 49. His journeys become longer as he ages, which is a testament of his cycling longevity.