While watching the Euro Cup final last week, a friend and I started debating the relative complexity of different sports. Soccer, we thought, was a relatively simple sport. Tennis and golf – while seemingly straightforward – were rife with rules surrounding etiquette and obscure situations. And football, with extremely subtle rules surrounding things like onside kicks and pass interference, was easily one of the most complex. But what do the data say?

Digging up the rulebooks for a given sport is fairly easy. Making sure that the comparison is done on an apples-to-apples basis, however, is not. The NFL rulebook includes a large number of case studies, as if referees are preparing for a degree in Law or Business. The tennis rulebook is fairly simple, but the “USTA code” – which governs rare situations such as a ball slipping out of a player’s pocket – nearly doubles the length of the official rules.

For the following summary, I did a simple word count on as consistent a basis as possible: no case studies, appendices, tournament regulations, or the like. Just the rules. On this basis, the most complicated sports were golf, hockey, and football.