Tobias J. Moskowitz and L. Jon Wertheim, Scorecasting: The Hidden Influences Behind How Sports Are Played and Games Are Won, Crown Archetype, 2011. [Amazon link]
"Defense wins championships". "In the zone". "Swallowing the whistle". "Icing the kicker (or shooter)". These and other sports clichés are common in the modern lexicon of fans, writers, players, and decision-makers. But are they accurate? And do the commonly held conjectures about modern sport have any basis in fact, or are they merely unsupported perception?
Toby Moskowitz, a finance professor at the University of Chicago, and Jon Wertheim, a senior writer with Sports Illustrated, have written a book that challenges these concepts in the style of similar books such as Freakonomics and Soccernomics. This book is more oriented toward North American sports, but there is enough of a sprinkling of findings from the European soccer leagues (and a drizzle from MLS) to merit a review on a soccer-related blog like this. Moreover, I am a strong believer in learning from the analytical challenges of other sports in order to gain insight about one's primary sport, and there are plenty of examples in the book to motivate questions by soccer analysts.
I deduce three themes in Scorecasting that are interest to people in sport and finance: omission bias, loss aversion, and opportunity cost.
Omission bias is the psychological term for people seeing acts of omission as either less harmful than an act of commission. It is very possible — as a matter of fact, it is very likely — that both acts are equally harmful, but most observers have less of an immediate problem with an act that doesn't take place. One example of this that the authors use are the decisions made by referees or umpires in the final critical stages of a sporting event. In the case of baseball, they use pitch f/x data to show that umpire strike zones do expand or contract at critical moments of the pitch count (3 balls no strikes or no balls 2 strikes). In other sports, the frequency of whistled fouls decreases as the match approaches its conclusion. Calls that are made during that time — think of the foot-fault that Serena Williams received at the US Open a few years back — are usually heavily criticized by fans and pundits as an example of the referee inserting himself into the game. What omission bias in sport indicates is that spectators and pundits want to see the players decide the game rather than match officials, and officials (unconsciously) take that into consideration when they make their decisions.
Loss aversion is self-explanatory — you miss the loss of what you have a lot more than enjoy the pleasure of winning something that wasn't yours. It is a powerful motivator in investing, in buying and selling, and in personal relationships (the authors told an example of how two economics professors used loss aversion in the form of $1,000 fines to lose over 80 pounds between them). It clearly applies in sport, whether it's going for a first down on 4th and short distance in American football, or focusing more on converting par putts than birdie attempts in golf, to pitch attempts in baseball in adverse pitch count situations. Loss aversion could explain the tactics employed by soccer coaches in the first leg of a two-leg series, especially when the away goals rule is in effect. In this situation, the away team might adopt a counterattacking approach, while the home team would seek to score goals while watching their back line (perhaps not press up too high). One could say that this is an artifact of the two-leg format, but coaches are equally or even more cautious in winner-take-all matches, with very few exceptions. It would be interesting to see what the data say in those situations.
The most interesting part of the book are the two chapters on home advantage in sport. The first fact is that home advantage is real across all sports leagues. The second is that in soccer, this advantage is most pronounced. Across domestic leagues all over the world, the home side wins 62.4% of the time (although I am unsure whether that percentage rolls in the percentage of matches that ends in a draw). Incidentially, the league with the highest home advantage over the last ten years is MLS at almost 70%, which doesn't seem to hold up in the playoffs. (Or does it?) Teams do play significantly better at home than away when one looks at the match statistics, and most soccer leagues do not have the issue of scheduling bias that other sports leagues have, since every team plays the other teams in the league the same number of times. The really fascinating finding is why teams have such a significant home advantage: referee bias.
Referee bias manifests itself, not in blatantly dubious decisions (at least among the honest refs), but in the number and frequency of calls toward both teams, and in soccer, the amount of stoppage time added to a match. The authors cited work by a group of Spanish economists that showed that in Spanish Liga matches, the amount of stoppage time given varied significantly depending on whether the home side was in a close game or a lopsided result. One can find the same results when comparing the number of red/yellow cards and penalties given in league matches across Europe. The explanation for this also has its roots in psychology, namely, "informational conformity". The idea is that the size and intensity of the crowd combined with the ambiguity of the situation influences the decisions that referees make, and in those situations, the decision will more often than not favor the home team. Such an explanation would make a lot of occurrences in football understandable, such as the fact that home nations in World Cup finals almost never lose (exception the Maracanazo), and the preference to play cup finals in neutral sites or (formerly) as two-leg affairs.
Moskowitz and Wertheim have a couple of chapters on how defense wins championships and how championships are almost always won with elite talent. The data are well-presented as in all the other chapters, yet I have some objections to their findings. The authors say that teams with better offensive records are more likely to win championships than teams with better defensive marks. I am not sure they are looking at the right measure, though. From my studies of goal distributions in domestic soccer leagues, it seems that a better indication of league success is the variance of goals or points allowed. It would be interesting to see if that observation holds up for other sports leagues. With regard to championships being won by teams with elite talent, I can think of two examples from MLS (Real Salt Lake in 2009, and Colorado Rapids last year) in which the league champion did not feature a player in the MLS Best XI. It could be less a characteristic of the league and more a characteristic of the playoff format, in which case the results of the new MLS playoff system will be very interesting.
The book concludes with a chapter on draft valuation, using the Dallas Cowboys' draft pick value chart as an example, to illustrate opportunity cost, two chapters debunking the myth of the "hot hand" or "streaks", which goes into random fluctuations, and the final chapter that attempts to explain the financial success of the perennially underachieving Chicago Cubs with some assistance from the concept of price elasticity.
At 255 pages, and twenty more for citations and an index, Scorecasting presents a lively and entertaining read about sport, economics, psychology, and statistics. Soccer is not the primary focus of the book — it's not even the third or fourth focus! — but it does present insight on interesting problems that should motivate research by the armchair and professional soccer analysts.