Blowing the Whistle on Home Field Advantage

Football player dives for the ball while teammate blocks a tackle behind him.

It’s easy to believe in the power of home field advantage. Teams regularly avoid resting their stars later in the season when jockeying for playoff seeding just to earn the right to play in front of their home fans. Look at football, where the term “12th man” has emerged to describe how fans act like an extra man on the field. In fact, the Seattle Seahawks retired the number 12 in honor of their raucous crowd.

Is home field advantage overrated, though? After all, the discussion is centered on professional athletes. As Hall of Fame quarterback Dan Marino said, “Sure, the home-field is an advantage – but so is having a lot of talent.”

There’s a lot of discussion about how much home field or home court benefits teams, if at all. It’s an old and undeniably complicated debate, as it brings in elements of psychology, statistics, and much more, to accurately tell what factors might bring the home team an advantage.

Is Home Field Advantage Real?

Looking at how much the home team wins is the most natural starting point for assessing whether home field advantage is a legitimate phenomenon.

A blog post on FiveThirtyEight, a website known for providing in-depth statistical analysis, compiled data on home team wins for regular season and postseason games from 2000 and 2017. It then calculated an expected winning percentage based on the quality of the two teams and if the game had been staged at a neutral site. Note how that element is most relevant for playoff games, as most sports play an equal number of home and road games.

Here are the results for Major League Baseball (MLB), the National Basketball Association (NBA), and the National Football League (NFL). Overall, MLB teams had the lowest home advantage of the three sports, and numbers didn’t improve in the postseason. Teams in the NBA and NFL had higher home advantages in the regular season and the playoffs.

  • MLB Home Field Advantage: Home teams won 54.0% of the regular season games (+4.0% expected differential) and 54.2% of postseason games (+0.0% expected differential).
  • NBA Home Court Advantage: Home teams won 59.9% of the regular season games (+9.8% expected differential) and 64.5% of postseason games (+4.1% expected differential).
  • NFL Home Field Advantage: Home teams won 57.1% of the regular season games (+7.0% expected differential) and 64.7% of postseason games (+11.8% expected differential).

Exploring Why There’s a Home Advantage in Sports

Overview

Many theories account for the home advantage in sports. Maybe loud crowds inspire players on home teams and break the concentration of those of the visiting teams. Or look at field conditions. MLB park dimensions vary, and NFL stadiums span natural and artificial grass as well as open, retractable, and fixed roofs. Yet another theory is based around travel. Players on the road might have a tougher time living, practicing, and playing in unfamiliar environments.

Based on a popular book, those theories are false. In 2012, behavioral economist Tobias Moskowitz and Sports Illustrated writer John Wertheim published “Scorecasting,” which failed to find persuasive evidence for those and other suggestions. The one factor they found that largely impacted home teams was referee bias. In crucial parts of the game, they reported bias in all three sports, as well as hockey.

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That finding isn’t the only piece of research pointing to referee bias. A seminal work from Thomas Dohmen was published in 2003 by the IZA – Institute of Labor Economics. His analysis of Germany’s top soccer league, the Bundesliga, revealed that the home field advantage was smaller in stadiums that had a running track around the soccer pitch. The advantage was larger when pitches lacked a track. In other words, home advantage is particularly noteworthy when fans are closer to officials.

“The social atmosphere in the stadium leads referees into favoritism although being impartial is optimal for them to maximize their re-appointment probability,” Dohmen said in the paper. “Conform with the preferences of the crowd, they lengthen exciting games and favor the home team by allowing most time when the home team is behind by one goal and by prolonging a drawn match when the home team is more likely to score next.”

Referee Bias in Each Sport

MLB

The MLB may have the weakest home field advantage out of all the major American sports, but it still offers a significant edge. As noted in “Scorecasting” and in an article from sports author and journalist Travis Sawchik, referee bias comes into play in the MLB. Here, it’s in the form of the strike zone.

“In baseball it turns out that the most significant difference between home and away teams is that the home teams strike out less and walk more — a lot more — per plate appearance than road teams,” according to Moskowitz and Wertheim in “Scorecasting.” Sawchik found the same trends for 2008-2015. Looking at balls and called strikes for that time span, he found that they were “quite strong” for favoring the home team.

NBA

Basketball may be the most obvious of the major three sports for referee bias.

A significant portion of fouls and infractions are judgment calls. From the charge-block call to how much contact players can make with their hands, a lot is left to interpretation and the flow of the game. Plus, referees in basketball have to have quick reaction time. They must make calls, in many cases, immediately after they happen. Compared to football, when a flag may be thrown at any point of a play for an infraction, NBA referees must act right away.

Take those factors and combine them with Dohmen’s insight about fan proximity to referees, and you have a recipe for referee bias. Fans are incredibly close to the action, more than any other major sport. As a result, their impact on home court advantage may be amplified.

NFL

Fans are not as close to the action in the NFL than the NBA, but there’s still perceived referee bias in the NFL. According to Michael Lopez, the director of analytics at the NFL, that truly comes into play in big game moments.

“If you look at the 15 most impactful, controversial calls in games over the past few years I think you’d find that maybe 14 of the calls went for the home team,” he told FiveThirtyEight. Lopez ultimately answered the question of what causes home advantage by saying that it’s unclear.

The Future of Home Field Advantage

There’s still a lot to learn about home field advantage. Debate surrounds exactly how much it matters and the underlying reasons for it.

Maybe referee bias is to blame. A decent amount of evidence supports that claim, although a lot of people still believe that home fans play a role in motivating their team. The idea also extends to how crowd noise disturbs visiting players’ concentration. Those types of factors are complex and difficult to study definitively.

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