Last December, I attended an NHL game at the Prudential Center in Newark, NJ between Metropolitan Division rivals New Jersey Devils and Philadelphia Flyers. The Devils jumped out to a quick 2-0 lead and then in the last six minutes of the first period, four fights broke out, prompting the PA system to blare out “Why Can’t We Be Friends” around the arena. The Devils went on to win 4-0 and Wayne Symmonds was ejected in the closing minutes.
Although this particular game was an extreme case, it got me wondering, is there a real increase in aggression in rivalry games? Or are people biased towards extreme events when making these statements? I decided to try to answer this question. To do this, I scraped data from Hockey Reference of every penalty awarded between the 2013/14 season and the 2016/17 season. The 2013/14 season was chosen as the start date because that is when the NHL adopted the 2 conference, 4 division format and this season was not included because of the introduction of the Golden Knights. I wanted to test the following:
1.) Do division rivalry matchups produce more penalty minutes and fighting majors than non division matchups?
2.) If the answer to question 1 is yes, is there a particular division that has extra feisty matchups?
First, I compared penalty minutes in divisional matchups versus non division matchups
We find that division matchups produce approximately 1.6 more penalty minutes per game than games outside the division. Given the extremely large sample size of games, we find that our T stat for this is around 10.
We conduct a similar analysis for the number of fighting majors:
We found that rivalry matchups induce an extra fighting major per every 10 games, or an extra fight (because fighting majors almost always come in pairs) every 20. This difference is not huge numerically, but we still find that it is statistically significant.
Now, we will look at which division has the highest number of penalty minutes:
We find that the Atlantic Division averages a penalty minute more per game than any other division. This makes sense, as this is the division that includes four of the six “Original Six” teams, which lends itself to some fierce rivalries.
In conclusion, we find that rivalry matchups do in fact lead to more fights and penalty minutes, and that the Atlantic Division has the fiercest matchups of the four NHL divisions. It would be interesting to see if any rivalries are huge outliers, and that lends itself potential to a future post.
If you have any questions for Andrew, please feel free to email him at firstname.lastname@example.org or reach out to him on Twitter @andrew_puopolo.