Scorecasting (26 page)

What about the size of the crowd? Recall the original study of the Spanish La Liga. The authors found that the bias in regard to extra time was even more evident when the crowd was larger. Similarly, the studies in the English Premier League, Italian Serie A, German Bundesliga, and MLS also found that referee favoritism was more apparent when attendance was higher. Maybe most interesting was the study conducted in Germany, where many of the soccer stadiums also house a running track that acts as a moat, separating the stands from the field of play. In those stadiums, the referees are more removed from the fans. Guess what? The bias referees usually exhibit for the home team gets cut in half in those stadiums but is the same as it is in other leagues for German stadiums that do not contain a track. In the three European soccer leagues we examined, attendance also had a marked effect on the number of red and yellow cards the visiting team received relative to the home team. Other studies have also linked attendance to penalties and fouls, showing that the bias in favor of the home team grows with the crowd.

What about the extra walks awarded to home teams and the extra strikeouts imposed on away teams by the home plate umpire? These, too, occur predominantly in high-attendance games and are not present in the games with the lowest attendance. The chart below shows the net strikeout and walk advantage to home teams from bad umpire calls, reported separately for the games with the lowest and highest attendance (bottom and top fifth of attended games). Although there is virtually no home team strikeout or walk advantage in the least-attended games, the highest fifth of attended games account for more than half of the entire strikeout and walk advantage given to home teams each season. In the highest-attended games, home teams are given 263 fewer strikeouts than their opponents. In the lowest-attended games, that falls to 33 fewer strikeouts. Similarly, the home team receives 93 more walks than the visitors from bad umpire calls in the most-attended games relative to the least-attended ones.

In the NBA, crowd size also affects the home-away differences, particularly for the more ambiguous calls. Recall how traveling is called 15 percent less often against home players. Looking at NBA games in the bottom fifth of attendance, this discrepancy goes down to 6 percent. But if we look at the most-attended games, the home team is 28 percent less likely to be called for traveling.

In the NHL, the bigger the crowd, the more penalties, fouls, and close calls that go against the visiting team, and once again, the effects are greatest for more ambiguous calls. Even in the NFL, in which most games are sold out, the home-away discrepancies in penalties and turnovers increase with crowd size. With virtually every discretionary official’s call—in virtually every sport—the home advantage is significantly larger when the crowd is bigger.

In fact, in the least-attended games in each sport, the home field advantage all but vanishes. In MLB, if you look at the 20 percent least-attended games, the home field advantage is only 50.7
percent. In other words, home and away teams are about equally likely to win when the crowd is small. In the one-fifth of games with the highest attendance, however, home teams win 55 percent of the time in MLB. In the NBA, the least-attended games are won by the home team only 55 percent of the time, and the most attended games 69 percent of the time. In the NHL, the home team wins only 52 percent of the time in the lowest-attended games but 60 percent of the time in the highest-attended games. And in European soccer, the home team wins 57 percent of the time in the lowest-attended games and an astonishing 78 percent of the time in the highest-attended matches.

Wait a second, you might say. Doesn’t this stand to reason? After all, crappy teams draw crappy crowds, so the games with the empty seats usually involve the worst teams. Never mind official bias; just look at the standings. You’d expect the Pittsburgh Pirates or the New Jersey Nets—lame teams, lame crowds—to win fewer home games than, say, the Boston Red Sox or the Los Angeles Lakers. True, but even after adjusting for the strength of the team we find similar effects. Also, it doesn’t matter as much as you might think, because when a bad team hosts a good team, attendance often spikes. When LeBron James and the Miami Heat visit Memphis or Milwaukee, the crowds swell. The worst-attended games usually involve two terrible teams, and the most-attended games feature two great teams. So it turns out there isn’t much of a difference in ability between the two teams in either case.

Still not convinced by the psychological explanation for referee bias? Consider a final study, this one performed in 2001. Researchers recorded videos of soccer matches, focusing on tackles during the game, and showed them to two groups of referees. The first group was shown the tackles with the crowd noise audible. The second group was shown the same tackles with the crowd noise muted. Both sets of referees were asked to make calls on the tackles they saw. The referees who watched the tackles with the crowd noise audible were much more likely to call the tackles
with
the crowd. That is, tackles made against the home team (where the crowd complained loudly) were more likely to be called fouls and
tackles made by the home team were less likely to be called fouls. The referees who viewed the tackles in silence showed no bias.

You probably guessed correctly which group of referees made calls consistent with the actual calls made on the field. Yes, the ones who could hear the crowd noise. Not only that, but the referees watching with sound also reported more anxiety and uncertainty regarding their calls, consistent with the stress they felt from the crowd. Imagine how much more intense that stress would have been if they had been on the actual field of play.

But perhaps the most convincing evidence for the effect of crowds on referees occurred when
no fans
were present. On February 2, 2007, supporters of two soccer clubs in Italy—Calcio Catania and Palermo Calcio—clashed with each other and police. It was a typical hooligan-induced riot, and following the episode the Italian government forced teams with deficient security standards at their stadiums to play their home games without
any
spectators present. Two economists (and soccer fanatics) from Sweden,
Per Pettersson-Lidbom and
Michael Priks, collected the data from the 21 soccer matches that were played before empty bleachers.

What they found was amazing. When home teams played without spectators, the normal foul rate, yellow card, and red card advantage afforded home teams disappeared entirely. Looking at the same team with the same crew of officials, the authors found that when spectators were no longer present, the home bias in favorable calls dropped by 23 to 70 percent, depending on the type of calls (a decline of 23 percent for fouls, 26 percent for yellow cards, and 70 percent for red cards). That is, the
same
referee overseeing the
same
two teams in the
same
stadium behaved dramatically differently when spectators were present versus when no one was watching.

When the economists also looked at player behavior, they found that, unlike the referees, the players did
not
seem to play any differently when the crowd was there yelling versus in an empty, silent stadium. Home and away players shot the same percentage of goals on target, passed with the same accuracy, and had the same number of tackles as they normally do. The absence of the crowd
did not seem to have any effect on their performance. This is in keeping with what we saw for NBA foul shooters, hockey penalty shots, and MLB batters and pitchers: Crowds don’t appear to have much effect on athletes.

So it is that we assert that referee bias from social influence not only is present but is
the leading cause of the home field advantage
.

We started with three questions that any explanation of the home field advantage must address: (1) Why does it differ across sports? (2) Why is it the same for a particular sport no matter where the game is played? (3) Why hasn’t it changed much over time?

To answer the first question, if the refs are responsible for the home advantage, it must be the case that referees are more important or have more influence in some sports (say, soccer, in which home teams have the greatest success) than in others (such as baseball, where the advantage is weakest). As it turns out, this is precisely the case. In soccer, the official has an enormous influence on the outcome of the game. One additional penalty, free kick, or foul can easily decide a game, in which one goal is often all that separates the two teams. In basketball, which has the second highest home team advantage, the official could call a foul on almost every play. By contrast, the umpire’s role in baseball is limited relative to other sports. Most plays and most calls are fairly unambiguous; a home run is a home run—either it cleared the fence or it didn’t. Most force-outs are not close. Sure, the umpire has discretion over called balls and strikes, but more than half the time the batter swings, eliminating umpire judgment.

In addition, crowd size, which we contend affects referee judgment, has more influence in the sports with the greatest home field advantage. Crowd size matters most in soccer (the sport with the highest home field advantage) and least in baseball (the sport with the lowest home team winning percentage) and is somewhere in between for the other sports. This is also consistent with referees mattering more in some sports (soccer) than others (baseball).

To answer the second question, referee bias also explains why
the home field advantage is the same for a particular sport no matter where it is played. Whether baseball is being played in the United States or Japan, whether it’s basketball in the NBA, WNBA, or NCAA or soccer in France versus South Africa, the rules and, more important, the role of the referee are essentially the same, no matter where the game is played.

Finally, to answer the third question, referee bias also explains why the home team’s success rate hasn’t changed over a century. Although sports have altered their rules over time—raising and lowering the pitcher’s mound, introducing a shot clock and the three-point line—the official’s role in the game hasn’t changed much. Umpires still call balls and strikes, referees still call fouls and penalties, and for over a century these calls have been made by human beings—none of them immune from human psychology.

Although we will never be able to measure or test all the decisions an official makes, if we can see that some biased judgments are being made, it is likely there are other biases going the home team’s way that we don’t see. Think of the father who comes home early from work and catches his teenage daughter kissing her boyfriend. He’s upset about the kiss, but he’s more upset about what else she might be doing when he doesn’t happen to be looking.

Knowing what we now know, let’s revisit that Cubs-Brewers game, the ten-inning affair that ruined a summer day for Jack Moore of Trempealeau, Wisconsin. You wouldn’t deduce this by scanning a conventional box score or watching a
SportsCenter
highlight. But after revving up the Pitch f/x results, it becomes clear that when the umpire erroneously called a ball on a 3–2 pitch in the bottom of the tenth inning, enabling the winning run to score for the hosting Cubs, it marked the culmination of an afternoon filled with unfavorable decisions against the visiting Brewers.