Following the complaints of dirty play in the Michigan-Michigan State game last weekend, the Wall Street Journal counted the number of unsportsmanlike conduct, late hits and other roughness calls in the last five meetings of forty rivalry games. UNC showed up in two of the nine most penalized rivalries, with their games against Duke being the second most (5.2 penalties per game) and the ones with N.C. State (3.4). In both match ups, UNC has generated the majority of the penalties, 69% against Duke and 59% against State. So what gives?
Well, I've long argued that the UNC-Duke football rivalry is fiercer than you would expect from its complete lack of prominence, but I don't think that's the story here. I would put forth that it's a combination of two factors. One, the games have been close, and as such of exceedingly poor quality. UNC's average margin of victory in the five games studied was just over six points. Duke, being Duke, was exactly stepping up for those games, so there was a lot of bad football being played. And bad football leads to penalties.
My other thought goes back to the economics study of home-field advantage. Refs' calls are very affected by crowd noise, and rivalry games have the most crowd noise... unless it's something sad like UNC-Duke. That's why I'm not that surprised that only one other rivalry (Georgia-Auburn) topped five penalties per game. A ref isn't going to want to insert himself into a tight, loudly cheered game unless the penalty is egregious. Something as meaningless as UNC-Duke though? It's not exactly a white-knuckle game.
And as for N.C. State? UNC's lost the last four of those five. And now we have a reason – the refs are biased. After all, when our team is penalized, it's poor refereeing. When their team is, it's because their incredibly dirty players who have no business being on the field.