Goal Production In Six Leagues, Or: Are the Eredivisie and Ligue 1 Different?

Here's a (possibly) puzzling factoid of the day. Together with Benjamin Leinwand, I've been looking at goal production in different leagues over the last 15 years, give or take. And one of the (to us, at least) interesting and puzzling patterns has to do with how many goals are scored per match in the biggest European leagues - including the Bundesliga, La Liga, Serie A, the EPL, Ligue 1, and the Eredivisie. Since we've just started digging into the data, we thought we'd brainstorm publicly and share some of the things we see.

The data are totals by season and league. To provide a baseline, across the last 15 seasons and across the six leagues, the average number of goals scored per match is 2.68. During this time, the lowest number of goals was recorded in Ligue 1 in 2006/7 at 2.13; the highest was 3.27, achieved by the Eredivisie in 1998/99. Added up over the course of a season, that's a pretty distinct difference. And these minimum and maximum numbers for Ligue 1 and the Eredivisie do not seem to be an accident; as it turns out, these two leagues exhibit goal production patterns that are systematically different from the other leagues. Take a look for yourself.

Specifically, while Serie A, La Liga, and the EPL all have average goal totals of around 2.6 per match over the past 15 years (2.607, 2.652, and 2.603, respectively, to be precise), Ligue 1 and the Eredivisie look fundamentally different: the average for goals per match comes in at 2.331 for Ligue 1 but 3.023 in the Eredivisie. These are noticeable differences that beg for an explanation or at least are worth thinking about. So what is going on here?

One might argue that Ligue 1 is a better league and that scoring should be harder in better leagues. But this wouldn't explain the difference between the French league and the biggest leagues (the Big 4). And what about the Bundesliga? It has higher goal totals than the other top leagues at 2.868 per match, but this is nowhere near Eredivisie levels.

As always, one possibility is that there are a few unusual (outlier) seasons that produce these overall patterns. To see if that is the case, we took a look at all data points (season average); put in a graph, these look as follows.

Clearly, there is cross-seasonal variation, with the leagues' goal averages sometimes overlapping in their distributions. That is, if we look at average goals in these leagues in any one year, we may see one of the leagues on top and another on bottom. But to us, the more remarkable pattern is that, considered over the long haul, each of the leagues seems anchored in its statistical place, with Ligue 1 at the bottom and the Eredivisie on top.

So are these leagues different from one another, statistically speaking? Our tests confirm that they are. Specifically, our pairwise tests of comparisons of means across the leagues (the so-called Sidak, Bonferroni, and Scheffe adjustments) reveal the following: According to all three tests

• the Eredivisie is significantly different from all other leagues
• the Bundesliga is significantly different from all other leagues
• Ligue 1 is significantly different from every other league
• the EPL, La Liga, and Serie A are all extremely similar

The question, of course, is why. Feel free to suggest possible explanations - we won't speculate right now, but we have some of our own suspicions, which we'll be happy to share over the next few weeks.