A few days ago, I wrote about patterns in referee decisions in Major League Soccer, with a focus on fouls and yellow cards. In international comparison, MLS referees have called fewer fouls than other leagues, suggesting either more fair play or less involved referees (for whatever reason). Since that analysis, we have had a rough weekend in MLS, with Seattle's Steve Zakuani breaking two bones in his leg and 2010 MVP David Ferreira of FC Dallas sustaining two fractures in his ankle. While I don't have the foul statistics for the weekend or want to suggest that this weekend was particularly violent, the conversation about referee quality in MLS is worth continuing, if you ask me.To make that conversation more productive, it's good to know some of the facts about MLS foul patterns, so I went out to look for some more (beyond the ones I already posted). In particular, I was curious to find out if MLS foul averages have always been so low or if this is a more recent development.
Thankfully, I didn't have to look too far to find out; here are trends in fouls called in MLS provided courtesy of the Climbing The Ladder blog.* It shows the average number of fouls committed and fouls suffered per match (the fouls committed category records slightly higher numbers because not all fouls involve the other team - think handball or swearing at the referee).
Clearly, average foul totals by match are way down, and they are at their lowest levels in the history of the league. Not only that, since recording a high point in the 2000 season, when the number of fouls fouls committed and suffered was around 33 per match, they have been on a consistent and fairly steep decline to around 20 (suffered). That's a huge decline, percentage-wise, in the neighborhood of almost 40%. We're not talking short-term fluctuations but a long-term decline over the course of a decade.
What can explain this pattern?
(a) the league wants referees to allow more continuous play to please spectators; or
(b) the quality of referees is lower in MLS than other leagues; or
(c) play in MLS is fairer than elsewhere.
I can't think of a good way to test (c), but think it's also the least likely explanation. After all, the league is thoroughly internationalized - in fact, truly globalized (remember this?) - so there's no good reason to assume that play is qualitatively different in this league than other leagues (unless we think that we would see fewer fouls in internationalized but lower quality leagues like MLS more generally - I can actually think of good reasons to assume the opposite).
So how can we get a handle on possibilities (a) and (b) - that the league instructs referees to look for continuous play by invoking advantage or that MLS referees just aren't very good (relatively speaking)? Unless you have first hand knowledge of communication between the league and referees, (a) is hard to test directly. It's also contrary to the league's stated intentions to crack down on fouling. And testing possibility (b) is hard, too, since we don't have strong indicators of refereeing quality in league play beyond the old ocular test.
What to do? One thing we can do is start with some facts we do have access to in order to see if they can shed some indirect light on things. So one question we can ask is whether this season (and the last one) is exceptional; are there trends in how many fouls MLS referees award or is the level of fouls relatively stable? Clearly, it's not. Instead, fouls appear to have vanished. So this might be evidence for (a) - the only trouble with that explanation is that MLS does not make referee assignments, so far as I know. That's done by the USSF.
So my next hunch was that it had something to do with (b) - that is, referee quality. And my hunch went something like this: when a new league like MLS in a soccer culture without lots of professional referees expands, the pool of available referee talent quickly runs dry. While the very top officials may be good enough, the average or below average official isn't. And this should be particularly problematic as the league improves while expanding, forcing inexperienced referees to call an ever better (and faster) quality of play.
So one thing we should see is a connection between the number of games the league needed to find referees for (the number of matches in a season) and the average number of fouls. Here's what it looks like when you plot fouls suffered per match by the number of matches in a season since 1996.
Lo and behold there is an extremely high correlation between the two (at -.81). That is, as the number of matches in MLS increased, the average number of fouls called by referees went way down (this correlation is similarly high at -.77 when we look at fouls committed).
Of course, this could be an accident, but what would explain this? One way to test this at the level of referees is to see if more experienced referees - those asked to referee lots of matches, presumably because they are good refs - call more fouls. To see if this is the case, I plotted the number of matches an individual refereed by the average number of fouls that referee called in the 2010 season. I also superimposed a linear trend line to show the pattern in the data.
The correlation is weak and not what I expected. If anything, it appears that the referees in charge of more matches call slightly fewer fouls. Of course, this is not conclusive evidence, but it also does not solve the mystery of low foul totals.
Something else must be going on; and that "something" is likely to have something to do with the dynamics of the match itself (for a great first look at the timing of yellow cards in a match, read this). You may remember from another analysis that there is a connection between the number of fouls a team commits in a match and the number if suffers - teams appear to play tit for tat, with more fouls by one team begetting more fouls by the other.
So the puzzle persists, and the issue of referee quality is also real and unlikely to go away soon. So why do leagues use exclusively home-grown referees? Wouldn't you want the best leagues to have the best referees and the quality of refereeing to grow along with the quality of a league's play, as in MLS? Maybe it has, and the numbers just don't show it. That's always possible. But maybe it hasn't, and that would be a problem. Ask Zakuani and Ferreira.
* The numbers are slightly different from what I have reported before, presumably because of slight differences in data collection techniques (these data are from the Elias Sports Bureau, MLS' official data provider; my data are from ESPN.com).
