And for other professions? Would the quality of teaching, for example, go up or down if professors were unionized?  

In a recent interview with Daniel Benson of The Pacific Standard, the disgraced cycling legend Lance Armstrong talked about the difference between cycling and other professional sports:

Well listen, the biggest difference between cycling, football and tennis is the players’ union, an athletes’ union. We have no voice, no unity. There are guys all over the place. Those sports, major league sports, they’re not letting that happen and the owners wouldn’t allow it to happen. Whereas we’ve [cyclists] just been living in the Wild West. The riders have no rights, ASO [the body that organizes the Tour de France] continues to make millions, the teams don’t own anything. The only thing a team owns is its current contract, and when that’s up you’re fucking done. You might have a couple of buses and a truck. There’s no equity and value. It’s a fucked up business model.

Doesn’t Lance Armstrong have a point?