But why is there a home field advantage? Many people assume that athletes simply play better when their fans are cheering them on, or at least that the visiting team doesn't play as well without crowd support. Some think the visiting athletes lose an edge from traveling long distances, eating out and sleeping away from home. Some fans figure that home teams simply are more comfortable playing in their home environment.
In fact, according to Moskowitz and Wertheim, none of those are a factor in the home field advantage. Instead, it's the refs (or, in baseball, the umps).
Moskowitz, a professor of finance, and Wertheim, a writer for Sports Illustrated, carefully dissect a slew of statistics to show that referees and umpires are influenced by home fans into giving a slight – but signifcant – edge to home teams. The home teams are called for fewer rules violations, and get the edge in close calls.
Consider:
- In soccer, referees give more "added time" at the end of the game if the home team is behind, but less if the home team is ahead. Home teams also are called for fewer penalties, and receive fewer red (ejection) and yellow (caution) cards. Notably, when two European soccer teams were forced by their league to play their games in empty stadiums because their fans had been too unruly, the home field advantage disappeared.
- In baseball, home teams strike out less and walk more than the visitors, especially when the game is close. "In crucial situations, the home team receives far fewer called strikes per called pitch than does the away team," Moskowitz and Wertheim say.
- In the NFL, the home team is penalized less and also benefits the most from the more valuable penalties, such as those that result in first downs. Home NFL teams used to have a big advantage in turnovers, but that has disappeared, the authors say, since the league began using instant replay to check the accuracy of referee decisions – itself a revealing development
- In the NBA, home teams get a huge advantage in calls that involve the most referee judgment, such as blocking fouls and palming, but no advantage in calls where the refs have little discretion, such as 24-second violations.
How do we know that visiting players don't just play worse, perhaps because they're tired or frustrated by the crowd? Because in the parts of the game where we can isolate performance, the authors show that there's no difference. Visiting teams shoot free throws just as well as home teams (yes, even with all those opposing fans waving their arms behind the backboard). Punters and kickers in football do just as well on the road as at home. In hockey shootouts, a situation where the referees have little role, home and away teams do equally well.
The authors further show that the distance teams travel has no effect on the home field advantage, nor does it matter when a team travels to play in a different climate, such as when the Miami Dolphins play on "the frozen tundra of Lambeau Field."
Moskowitz and Wertheim say just one other factor plays a part in the home field advantage and it applies only in the NBA and the NHL. In those leagues, visiting teams play more games on consecutive nights than home teams. This does, the authors say, contribute somewhat to the home field advantage, but it's still not as significant as the referee bias.
The authors don't accuse referees and umpires of consciously favoring the home teams, but rather of subtly being influenced by screaming fans. And indeed, the more packed the stadium, the bigger the referee bias.
I can't say I'm pleased with the authors' conclusions, but they pile on so many statistical elements that it's hard to dispute. I was always raised to cheer for your team and leave the referees and umpires alone to do their job. But after reading "Scorecasting," I have to conclude that if you want to help your team, forget about shouting "Charge!" or "DE-fense!," and instead start yelling at the ref.
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