This season's Dutch Eredivisie was a fascinating championship to follow, not just because the storyline of Steve McClaren finding rehabilitation in FC Twente, but also because of the gaudy statistics of Ajax in finishing second. I had my doubts that the Pythagorean formula would be able to predict the total number of points in the face of such a skewed scoring record. Here's the league table with Pythagorean estimations included:
|SC Heracles Almelo||34||54||49||56||49||+7|
|Roda JC Kerkrade||34||56||60||47||44||+3|
|ADO Den Haag||34||38||59||30||34||-4|
|Willem II Tilburg||34||36||70||23||28||-5|
I did not expect the Pythagorean expectation to predict the total number of points very well in such a scenario, and my expectations turned out to be correct. Twente, Ajax, and PSV outperformed their projections by at least nine points. Ajax outperformed by 13 points — a difference of four wins. But look at the difference in predicted points between Twente and Ajax — it was just a point, as it turned out in the final table. Ajax lost the league title because Twente also played way over their heads during the season; the Tukkers scored 15 more points that their statistical expectation.
There could be a couple of reasons for the huge discrepancy in point totals. First, the scoring distribution for the top teams this season may have been more skewed than is typical for most domestic leagues. I took a cursory glance at the result matrix for the Dutch league and my first impression is that Twente had a more typical goal distribution but Ajax's goal distribution so heavily skewed that a Weibull distribution may not have been accurate. (I need to do a more extensive analysis to find out if that was indeed the case.) The second reason could be that the Pythagorean expectation does not take into account the spread (variance) of the scoring distribution. The variance corresponds to the scoring consistency during the season and could add a couple of points to the Pythagorean expectation. The approach is similar to that presented by Kerry Whisnant in his Pythagorean extension for baseball.
This year's Dutch league was characterized by a majority of teams with lopsided goal differences and a handful of teams with nearly even scoring and defensive records. Only five clubs in the 18-team top flight had goal differences between -10 and +10. Heracles appeared to have won more matches than were expected of them, but they earned their place in the European playoffs. At the other end of the table, Waalwijk (automatic relegation place) and Willem II (relegation playoffs) had poor seasons, but perhaps Sparta Rotterdam had a performance that was expected of them.
Essentially teams at the top of the table win more matches than might have been draws, while teams at the very bottom lose more matches that could have been draws. At least that observation held up in the Eredivisie this season.