Tuesday, January 18, 2011

The Distribution of Corners in the Big Leagues of Soccer: The 2010-11 Season To Date

Corner kicks are kind of like free kicks in the opponent's half: both are set pieces. They're also among the few moments in a match when teams have a real and predictable opportunity to score. And while I've been thinking about them for some time, I have not reported any systematic analyses of corners. Recently, one of the faithful readers of this blog asked about them, so I thought I'd start by taking a quick look at the frequency and distribution of corners so far this season in the four big leagues (Bundesliga, Premier League, Serie A, and La Liga). 

So, as of Dec.23, here's what the distribution of corners per match (and team) look like across the leagues.

What do we see?

First, a geek alert: The distribution of corners is not normal in any of the leagues; instead, it is right skewed in all four leagues (meaning that the average number of corners teams are awarded per match is to the right of the most common number of corners, or so-called mode, per match). This is not at all unexpected, given the relatively small number of corners teams are awarded in normal play. Because of the so-called law of small numbers, we could expect the distribution to become more "normal" or bell-shaped if we were to observe many more instances of corners in football. But the skew is not particularly large.

Second, what does this mean practically? Teams experience slightly more matches with just a few corners than matches with lots and lots of corners, but this difference is small since the most common number of corners per team and match that have occurred across the leagues this season is the same in every league (in case you're wondering, it's 5), and this number is not very different from the average number in each league.

Third, the range goes from a minimum of 0 (which has occurred in every league) to 14 (La Liga), 15 (Bundesliga), 16 (Serie A), and 17 (EPL).

So what is the actual average number of corners teams are awarded per match? Take a look.

As you can see and as is the case with other soccer statistics, the leagues are very similar when it comes to how many corners teams are awarded in an average match, registering between 5 and 5.5 corners per match:

Bundesliga: 5.05
EPL: 5.52
Serie A: 5.49
La Liga: 5.37

What about a home team advantage in corners? If we presume that corners are a reflection of offensive play, we would expect home teams to produce more corners. And that's exactly what we see.

There is home team advantage in every league, but this advantage is not of exactly the same size across leagues. The home team advantage is largest in La Liga, where home teams can expect about 1.5 more corners than away teams (6.11 v. 4.63) and smallest in the Bundesliga, where home teams generate slightly fewer than one more corner than away teams (5.5 v. 4.6), making the Bundesliga a more even league in that regard (the gap in the EPL and Serie A is about 1.25).

Soon I'll look into corners in a bit more detail. In the meantime, stay tuned.