Once upon a time, it was statistically accurate to say that sports teams playing on their home turf won more games than visiting teams. For decades, this was true. 

Spoiler alert: this is no longer the case. The home field advantage is disappearing, especially in professional sports.

To understand the shift, we first need to understand why the home field advantage is a phenomenon in the first place. It’s a question that’s engaged scientists across disciplines, from statisticians to social and sports psychologists. 

The root causes, researchers have determined, may involve factors related to travel, posited to affect the physical experience of the players. But it’s the support of the home team’s crowd — overwhelmingly seen as a psychological force — that’s the biggest factor in the home field advantage, and is directly tied to its decline today. 

What Is Home Field Advantage?

Home field advantage is a well-recognized phenomenon in team sports, referring to the benefits that the home team enjoys over the visiting team. 

Researchers studied home field advantage in a range of sports and venues — from individual to team sports, as well as across the high school, college, and professional levels — to determine if it held true everywhere. 

In all of these, scientists found that the home team won more than half the time and as often as 70 percent of the time.

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How Does Home Field Advantage Work?

Researchers have determined that the root causes of home advantage may involve factors related to a familiar environment, no travel fatigue, and crowd support.

Familiarity Factor

Playing in familiar surroundings, where athletes are used to the field, stadium, or arena, helps in better performance. 

Though it was widely discussed by teams as a contributing factor, researchers early on dismissed familiarity with the field or court — dubbed the “learning factor” — as an issue that could alter the outcome of a game. 

Studies concluded that knowledge of the venue was not a determining factor most of the time. Still, there are exceptions in certain cases, such as the Green Monster at Fenway Park, a green wall in the outfield that is so “unique,” say non-Red Sox players, that they just have to learn to “get used to it.”

Travel Factor

Meanwhile, “travel factors,” such as the physical effects of flying and time zone changes, were found to be contributors to the home field advantage.

Altitude changes — like playing an NFL game against the Denver Broncos at Empower Field at Mile High stadium, which sits an elevation of 5,280 feet — also had a noticeable impact, particularly when the home team is more acclimated. 

In fact, Denver-based teams were found to have the largest home advantage in the NBA, NFL, and the MLB, according to a statistical analysis published in 2017 in The Annals of Applied Statistics.

Crowd Factor

But scientists ultimately found that “crowd factors” — that is, the support of the home crowd — were the prime reason for home field wins. Perhaps surprisingly, it’s not really about crowd energy or the volume of their cheers. 

Studies suggest that fan enthusiasm is a positive motivator for home team players, but the crowd’s excitement also carries with it a negative energy known as the “cost of failure” factor: The home team’s fear of losing at home (and the ridicule that could follow) may motivate players to focus on avoiding failure rather than “striving for victory.” 

And further, there’s research that shows players tend to perform more poorly when their fans expect success.

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How Do Fans Really Affect the Game?

The key element here — and the one that’s led to the more-recent decline of the home field advantage — is the influence the hometown crowd has over officials. 

How Do Referees Affect the Game?

Statistical analyses of called plays, like traveling in basketball or penalties in hockey, show that officials call in favor of the home team and against visitors at a statistically significant rate, according to Konstantinos Pelechrinis, an associate professor of computing and information at the University of Pittsburgh.

Similarly, Yale behavioral economist Tobias Moskowitz, who penned Scorecasting: The Hidden Influences Behind How Sports Are Played and Games Are Won, agrees that refs may be the biggest contributors to home-field advantage. Psychologists who have studied the analytics say the influence crowds have over officials is subconscious, not intentional. That is to say, it’s not a conspiracy, but simply a consequence of being human.

How Calls Affect a Game’s Outcome?

Nevertheless, how a play is called can have a profound effect on the game’s outcome.

“Clearly, it only takes 2 or 3 crucial decisions to go against the away team or in favor of the home team to give the side playing at home the ‘edge,’” write the authors of a study that took a look at decades of research on the home field advantage.

Pelechrinis’ analysis suggests those incorrect calls, or non-calls — when the ref doesn’t call a foul, for example — take place during the most critical moments of a game.

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Why Is Home Field Advantage Declining?

There are a number of changes that have taken place that have driven the dwindling effect of the home field advantage.

In part, it may be a consequence of how the rules of the game have changed in the 21st century. In 1999, for example, the NFL instituted instant replay and also a rule that allows coaches to challenge a ref’s call. The rule change made a difference: By 2020 the home field advantage in football dropped to roughly 52 percent. Similarly, a rule that allows coaches to challenge calls in the NBA has resulted in a decrease in the home field advantage.

There’s also been advances in sports medicine and logistics that have reduced the negative impact of travel. Players wear compression socks, for example, and have learned to increase their water intake. And teams themselves have begun to reallocate money to bring the luxuries of home on the road with them — including massage therapists, private chefs and even their favorite brand of ketchup. 

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This article was originally published on April 7, 2022 and has since been updated by the Discover staff.