I've been traveling to Switzerland, Germany, and now England these last few days, so I thought it was only fitting to post the analysis below from London where I am currently enjoying the good weather and great company of friends and colleagues. When having conversations, especially here in England and over a pint or two of good beer, it's not unusual to hear complaints about leagues becoming too unequal. Usually these complaints are couched in terms of fairness, and they tend to come from supporters or officials of clubs that aren't doing as well as they would hope. But none of this means the complaints don't have merit.
To see if there's anything to them, some data Benjamin Leinwand and I have been collecting may help us out, I think. Initially, Benjamin and I wanted to get a sense of overall levels of parity in various leagues and to put them in perspective. So we started by examining levels of competitive balance in six European leagues with data for the past 15 years. We measured balance in a league based on wins and with the help of the Gini coefficient and the so-called Standard Deviation. The data showed that - considered over the entire 15-year period - the Dutch Eredivisie has been the most imbalanced league, while the French Ligue 1 has been the most balanced. The data also showed two groupings, with Ligue 1, the Bundesliga, and La Liga exhibiting more and the Eredivisie, EPL, and Serie A less balance.
Of course, there are different ways to measure competitive balance, and we'll provide some analyses of whether this matters before too long.* In the meantime, though, I thought I'd point out that what you find has a lot to do with where you look, and that's true when it comes to understanding league (im)balance, too. There are different ways of slicing the data on leagues and each gives you a slightly different vantage point on where leagues are or are headed. Here's an example. The good thing about combining 15 years of data when looking at league balance is that we can avoid focusing too much on recent events that may or may not be typical. But there's a downside to this: by averaging over a longer time span, trends get lost in the shuffle. It seems to me that both are important - we want to know if the Bundesliga is more balanced than, say, the EPL, but we don't want to make sweeping generalizations by looking just at last year's results.
But we also want to know if a league has become more or less balanced in recent years - that is, what has happened to parity over time. Is the Eredivisie's or the EPL's lack of balance (compared to the other leagues) a recent development, or does it reflect a long-standing pattern? To answer these kinds of questions and get a sense of the dynamics of competition in the six leagues, we took a look at trends over time and plotted the annual Gini and Standard Deviation scores since the 1994/95 season. The picture looks like this.:
The first point is that some leagues show very clear upward trends. The trend is most obvious in the case of the EPL, where we see an ever increasing imbalance in the league that started as far back as 1997. And this trend is apparent, regardless of which measure of imbalance we use.
The numbers show that the Premiership is significantly more imbalanced today than it was 5, 10, or 15 years ago. But it does not seem to be the only league with a growing competitive imbalance. The Bundesliga, too, seems to have crept upward ever so slightly, and so has La Liga very noticeably since 2002. Interestingly, the Eredivisie's high level of imbalance and Ligue 1's high level of parity do not seem to have changed much over time.
And the trends are statistically significant: when we estimate a regression model of Gini or Standard Deviation with time as the independent variable, we find significant and positive linear trends (p<.05) in the EPL (for the Gini coefficient as well as the standard deviation), and for Serie A (for standard deviation of wins). The coefficients for La Liga are positive, too, but significant only at the .10 level (two tailed tests of significance, in case you were wondering). So what we can say, based on these data, is that the Premier League has become significantly less balanced over time, and that La Liga and Serie A also have become more unequal, but the trends there are not as clear cut - in the case of Serie A only with regards to one measure of parity and in the case of La Liga to a lesser extent (statistically and substantively speaking).
Now that we know the overall historical levels of balance and trends over time, let's get to the fun stuff most fans really care about: what do the numbers tell us about which of the leagues was most imbalanced in 2010/11? Take a look:
Regardless of whether we measure league balance with Gini or Standard Deviations, we currently have two sets of leagues when it comes to parity. On one hand, there's La Liga, the Premier League, and the Eredivisie, one of which was imbalanced to begin with (Eredivisie) and two of which have become more so over time (La Liga, EPL). On the other hand we see significantly lower and virtually identical levels of imbalance in Ligue 1, Serie A, and the Bundesliga for the 2010/11 season. Looking at standard deviations alone (below), the Bundesliga was in a league of its own, recording the highest level of parity of all the leagues last year.
So what does this mean? Assuming that levels of imbalance in the Premier League are too high or are in danger of being too high (and some people would disagree with either assumption), it tells us that Manchester City and Chelsea are not really the problem, or not the only problem the league has. The trend toward competitive imbalance in the Premier League started quite some time ago and well before Roman Abramovich and Sheikh Mansour appeared on the scene. At the same time, I do wonder how much more of a league of haves and have nots the league wants to become (or remain). And the Premiership is not alone; some of the other leagues also seem to be on the verge of becoming significantly more unequal - in particular La Liga - and another - the Eredivisie - already is very unequal. And while the Bundesliga appears to be the healthiest league at the moment (financially speaking), it's not clear that this is necessarily connected to the level of competitive balance. After all, one of the sickest leagues (Serie A) is just as balanced but not doing nearly as well.