Most professional athletes don't earn big money. Rather like music, a very few make it in the big leagues. Of the rest, some find steady work in minor teams; many, many others struggle to get by combining their passion with casual day jobs.

If your sport isn't one of the few that can command massive advertising dollars, then there may be no pay at all. The value chain is very clear: all high athlete salaries are ultimately funded by advertisers wanting access to consumer eyeballs.

Overlay all this with the very short effective career, the near-absence of post-athletic marketable skills, and the devastating effect of injuries, and you'll find athletes are statistically underpaid over their lifetimes.

Statistically underpaid compared to what?