I’ve been researching penalties called against home teams versus penalties called against road teams. In a perfectly fair system these 2 would generally be equal, but game officials are human, too. They respond (even if subconsciously) to peer pressure of the crowd.

I used the database a pro-football-reference.com for this study. The first search was to find how many games in the 2014 season did the home team get 10+ penalties called against it, and then try the same search, but this time for road teams.

2014 season – home teams getting 10+ penalties = 32
2014 season – road teams getting 10+ penalties = 43

So, 75 times it happened in the 2014 season (including playoffs), but 43 of the 75 (57.33%) were to road teams. Might not seem like much, but it really is. Home teams were 153-112 (ignoring ties) in 2014, which comes out to 57.74% home winning percentage. Coincidence?

Let’s look at penalty yardage now. The query this time is how many times the home/road team is penalized for 125+ yards in penalties.

2014 season – home teams getting 125+ yards penalties = 1
2014 season – road teams getting 125+ yards penalties = 6

A team getting 125+ yards in penalties only happened 7 times in 2014 (including playoffs), but 6/7 were road teams.

But, as we lower the threshold for penalty yardage, the gap closes (but is still in favor of home team).

Penalty yardage = 100+ yards
home teams = 15 (45.45%)
road teams = 18 (54.55%)

What does it mean? There is no question home teams have an advantage, as evidenced by the superior home team records, but I think most people assume the advantage is from familiarity with the arena (playing surface, facilities, etc.) and the extra motivation to do well in front of a boisterous home crowd, and all of this might well play a positive role, but I think a big part of the home advantage (and one that is often overlooked) is simply the penalty advantage.