When the Home Crowd Wins: The Science of Home Advantage

It is one of the most reliable facts in all of sport: teams win more often at home. Everyone knows it, athletes feel it, and the statistics confirm it across virtually every game on Earth. But for decades, no one could quite prove why — until a global pandemic accidentally ran the perfect experiment, emptied the world's stadiums, and revealed a surprising culprit hiding in plain sight.

Ask any sports fan and they will tell you, without hesitation, that playing at home is an advantage. It feels obvious. The home team has the roaring support of tens of thousands of fans; the away team has travelled, is far from home, and faces a hostile crowd. And the data backs the intuition emphatically: across almost every sport in almost every country, home teams win a clear majority of their games. Home advantage is one of the most robust, universal patterns in sport.

But here is the deceptively difficult question that lurks beneath that simple fact: what actually causes it? Why, specifically, does the home team win more? For a long time this was surprisingly hard to answer, because several plausible explanations were all tangled together and impossible to separate. Then, in 2020 and 2021, something happened that no scientist could ever have arranged on purpose — and it cracked the mystery open.

The four usual suspects

For years, researchers proposed four main factors to explain home advantage, and the trouble was that they all operated at once, making it nearly impossible to tell which one was really doing the work.

The first, and most obvious, is the crowd — the thousands of home supporters roaring their team on, thought to lift the home players and intimidate the visitors. The second is familiarity: the home team knows every quirk of its own ground, the exact dimensions and feel of its pitch or court, having played on it countless times. The third is travel fatigue: the away team has had to journey to the venue, sometimes across the country or the world, arriving more tired and disrupted than the rested home side. And the fourth is territoriality — the deep, almost primal instinct to defend one's own turf, which may raise the home players' aggression and drive.

Each of these is plausible. Each probably plays some role. But because they always occur together — the home team always has the crowd and the familiarity and the rested legs and the home turf, all at the same time — teasing apart their individual contributions was fiendishly difficult. To really test the crowd's effect, for instance, you would need to somehow have teams play at home, with all the familiarity and rest, but without the crowd. Under normal circumstances, that situation essentially never happens. And then, suddenly, it happened everywhere at once.

The experiment nobody wanted

When the COVID-19 pandemic swept the world, sport did not entirely stop — but for a long stretch, it was played in eerie silence, in vast empty stadiums with no spectators allowed. Across many countries, thousands upon thousands of professional matches, especially in football, were contested in front of no one. It was a tragedy for fans and a strange, hollow spectacle. But for scientists studying home advantage, it was an extraordinary, once-in-a-lifetime gift: a natural experiment, conducted simultaneously across the globe, in which one variable — the crowd — was removed while everything else stayed the same.

Now the crucial test could finally be run. The home teams still had their familiar grounds. The away teams still had to travel. Territoriality was unchanged. The only thing missing was the crowd. So if home advantage was really about the fans, it should shrink dramatically in the empty stadiums. And if it was mostly about familiarity or travel, it should barely change at all. Researchers pored over tens of thousands of matches played before and during the pandemic, and the results were revealing.

The verdict: it's the crowd — and the referee

Home advantage did not vanish in the empty stadiums, but it clearly diminished — across many leagues, the home edge shrank noticeably, by roughly a third overall, with some competitions seeing home win rates tumble toward, or even below, the break-even point. This was strong evidence that the crowd is indeed a major driver of home advantage. Take away the fans, and a good chunk of the home team's edge goes with them.

But the most fascinating and specific finding was about how the crowd exerts its influence — and it was not, primarily, the way most people would guess. The single clearest effect showed up not in the players, but in the referees.

When researchers examined the decisions officials made, they found something striking. In normal times, with a packed home crowd, referees tended to favour the home team — awarding more fouls and more cards against the visiting side, giving the benefit of the doubt to the home players. But in the empty stadiums, this bias substantially disappeared. Without the pressure of thousands of screaming home fans, referees officiated far more evenly, and the excess of cards and fouls handed to away teams largely evaporated. The inescapable conclusion is that the roar of a home crowd unconsciously influences the officials, subtly pressuring them — no doubt without their even realising it — to make decisions that favour the home side. The crowd's most powerful weapon, it turns out, is not inspiring their own players. It is leaning, invisibly, on the referee.

This is a genuinely important insight, because it reframes what a home crowd actually does. We imagine the fans as a "twelfth man," spurring their heroes to greater effort. And there is truth to that — the studies also found that home teams were somewhat less dominant in play without fans, taking fewer shots and creating less, suggesting the crowd does give players a real lift. But a large part of the home crowd's measurable effect flows through the officials. Tens of thousands of people passionately demanding a decision genuinely makes that decision more likely to go their way. The pressure is real, and it works.

Familiarity, travel, and the supporting cast

If the crowd is the star of the show, the other factors play genuine but smaller supporting roles — and the empty-stadium experiment helped size them up too.

Since home advantage shrank but did not disappear when the crowds vanished, something other than the fans must account for the portion that remained. Familiarity is part of it: there is good evidence that knowing your own ground helps, and tellingly, teams tend to perform worse in the season when they move to a brand-new stadium they haven't yet grown accustomed to. Travel fatigue matters too, but the research suggests it mainly bites when the away team has to cross multiple time zones, disrupting their body clocks — a big factor in vast countries with continent-spanning leagues, but a minor one in compact competitions where every away trip is a short hop. Territoriality and the psychological comfort of being "at home" likely contribute as well, subtly boosting the home players' confidence and aggression.

There are other wrinkles, too. Altitude can be a powerful home weapon: teams based high in the mountains gain a real edge when lowland visitors, unused to the thin air, struggle to cope. And the effect of the crowd itself scales with its size and intensity — the bigger and more fervent the home support, the larger the advantage tends to be. Home advantage, in short, is not one thing but a bundle of overlapping effects, with the crowd — and its grip on the referee — as the largest single strand.

What it means for the games we watch

The science of home advantage carries a lesson that goes beyond sport. It is a beautifully clear demonstration of how powerfully social pressure can shape human judgement, even the judgement of trained professionals whose entire job is to be impartial. Referees are not corrupt, and they are certainly not trying to favour the home team — but faced with the overwhelming, emotional, unanimous roar of a huge crowd, their split-second decisions bend, just slightly, in the crowd's favour. None of us, it seems, is fully immune to the pressure of the mob, however much we believe in our own neutrality. It is why sports have increasingly turned to technology, like video review of contentious decisions, to try to insulate officials from exactly this kind of unconscious influence — with some success, though it hasn't been eliminated entirely.

For the fan, there is something quietly empowering in all this. The next time you're in a stadium, roaring alongside thousands of others, you are not merely a spectator. You are, in a small and measurable way, part of the contest — tilting the officials, lifting your team, and adding your voice to a force that genuinely helps decide the outcome. The home crowd's advantage is real, it is scientifically demonstrated, and a large part of it is powered by exactly that: the crowd. The pandemic's empty, silent stadiums proved it beyond doubt. When the fans came back, so did the roar — and with it, the invisible, decisive weight of the home crowd.

Sources and further reading

• Studies exploiting COVID-19 "ghost games" as a natural experiment (e.g., Wunderlich et al., PLOS One, 2021; and analyses in Scientific Reports and Economics Letters) showing home advantage reduced by roughly a third and the disappearance of crowd-induced referee bias in empty stadiums.
• Research on the four classical factors of home advantage — crowd support, familiarity, travel fatigue, and territoriality — and their relative contributions (e.g., same-stadium derby studies estimating the crowd's share at around 60%).
• Evidence that travel fatigue matters mainly across multiple time zones, that teams perform worse after moving to a new stadium (familiarity), and that home advantage scales with crowd size.
• Discussion of crowd-induced referee bias (more fouls and cards against away teams with fans present) and the moderating role of video review technology (VAR).