Understand Footy

Understanding home advantage

home town
First published in Inside Football
August 2011

By Mick Ellis

In 2000, a now famous experiment in the UK took 40 qualified soccer referees, split them into two groups and showed them footage of 47 incidents from a Premier League match between Liverpool and Leicester City.
The referees were asked to make decisions on the incidents as though they were officiating the game.
The first group watched the video with the crowd noise turned up; the second watched the vision with no sound.
Researchers then compiled the decisions of the two groups according to the proportion of fouls awarded to a) the home team, b) the away team, c) neither, d) uncertain.
The findings were clear-cut.
In the group exposed to the crowd noise, the referees’ decisions favoured the home team –- that is, the referees were much more likely to call the fouls with the crowd.
This group’s decisions were consistent with the calls made in the actual game.
In the group without the crowd noise, the same tackles were called quite differently.
On top of that, the referees exposed to the crowd noise reported higher anxiety and uncertainty about the accuracy of their calls.
The nature of the referees’ calls was also significant, as the study found that fewer fouls were called against the home team.
This fit with previous research in basketball showing that fewer fouls were given against “star” players at home.
The study concluded that referees’ decisions were influenced by the nature of crowd noise, and the human tendency to avoid crowd displeasure.
This unintentional bias has been demonstrated experimentally and statistically again and again, although no study has been completed into trends in the AFL.
It is now so widely accepted across professional sports around the world that many have taken counter measures, introducing technology, third umpires and the like.
Now a new book just published in the United States --
Scorecasting; The hidden influences behind how sports and played and games are won -– presents research that demonstrates this phenomenon almost entirely accounts for home-ground advantage, in every professional team sport.
Homeground advantage does vary between sports, although it does not vary markedly within the same sport, no matter the country in which it’s played.
The home advantage in soccer (around 65 per cent) is the same in every country, just as it is in cricket (60 per cent) and baseball (54 per cent).
In fact, say the authors, the degree of homeground advantage in a sport depends mostly on the degree of technicality in the rules and to what extent officials are called upon to make “judgment” calls (more prone to unintentional bias) rather than whistle for technical rule breaches (less prone).
In Aussie rules, as in all sports, homeground advantage remains an undeniable factor in deciding whether teams win or lose.
Figures show that in the AFL, home teams win about 57 per cent of games.
The advantage in any given week varies, of course, according to the strength of the home team. (At Skilled Stadium, over the past four years, Geelong is running at a 97 per cent winning ratio!)
But taken over the entire competition, over a period of years, the average advantage is around 57 per cent.
In 2010, this exactly matched the discrepancy between home and away free kicks (that is, 7 per cent more for the home side).
In 2011, frees for the home side exceeded those for the away side by 11 per cent.
The Scorecasting researchers investigated the standard explanations for homeground advantage.
Could it be the comforts of home, the familiarity of the arena, the absence of travel, the scheduling of back-to-back road trips (a killer for travelling teams in basketball), or simply to the greater crowd support urging on the players?
All of the above, perhaps?
Actually it’s none of the above. They found very little basis for any of those explanations in any sport.
For example, looking for a correlation between distance travelled to away games and success rate, the researchers compared national league soccer in Australia (where teams travel vast distances between the capital cities) and the Netherlands (where clubs are relatively close together), but detected no statistically significant difference in home advantage (around 65 per cent in both leagues).
The authors conclude that homeground advantage can be put down almost entirely to unintentional bias on the part of the officials.
Analysing data from soccer, American football, baseball and hockey, the authors demonstrate that in those sports that require more black and white technical adjudicating, homeground advantages diminish.
In those with more grey areas in the rules, the crowd comes into play.
And of course, it is most pronounced where crowds are one-sided, filling stadiums with home-team support.
This predicts greater bias at, say, Patersons Stadium packed out by Eagles fans –- as Richmond coach Damien Hardwick alluded to last week –- rather than at the MCG with an 80,000-strong crowd split between Collingwood and Essendon fans.
The psychology is simple.
“We’re convinced that the vast majority of, if not all, officials are upstanding professionals, uncorrupted and incorruptible, consciously doing their best to ensure fairness,” write the authors of
“They are not, however, immune to human psychology.
“Psychology finds that social influence is a powerful force that can affect human behaviour and decisions without the subjects even being aware of it.
“Psychologists call this influence conformity because it causes the subject’s opinion to conform to a group’s opinion.”
Scientific experiments repeatedly demonstrate this.
When umpires face enormous pressure – having to make a crucial call with a rabid crowd yelling in unison – it is natural to want to alleviate that pressure.
Also, in an uncertain “grey area” call, the crowd can give the umpire a cue. (The crowd booming “Ball!” makes an irresistible case for the official.)
Contrary to mainstream opinion in football, this research demonstrates that officiating does indeed influence the outcome of games.
“I’ve never known the umpiring to determine the outcome of a football game,” states AFL rules committee member Kevin Bartlett, at most opportunities.
On close analysis, that position appears open to question.
This research demonstrates that umpiring – decisions made or omitted – does indeed determine the outcome of sport, to a far greater extent than previously appreciated.
As well as the common “Ball! Yes!” calls in AFL, think of the run of free kicks that seems to go the way of a team with a “run on” – each one accompanied by the crowd’s roar of approval.
Think of the momentum of a home team pegging back a lead in the final quarter in front of a rapturous stadium and the pressure on the umpires to call free kicks in their favour.
Also, the closer the crowd sits to the arena, the greater the demonstrated effect in overseas studies.
The authors try but find no evidence that crowd support influences players’ performance to any measurable extent.
AFL Umpires Coach Rowan Sawers says he is unaware of the research but that the emphasis in coaching the AFL umpires is on “getting it right”.
“We train our umpires to stay involved in the game, to concentrate and focus on being in the right position and make the right calls so the crowd noise is just background noise,” he said.
“And that’s speaking from experience. When you’re involved in the game, you’re making split-second decisions and if the crowd roars you’ve usually already made the decision anyway.”
Scorecasting makes the point that very few fans consider they could personally do a better job than the players they are cheering on. But most think they could do better than the umpires.
This ignores the fact, however, that officiating professional sport requires some rare aptitudes.
Most successful umpires are also high-achievers in other fields.
The AFL umpiring ranks contain several lawyers (eg. Stephen McBurney, Justin Schmitt, Shaun Ryan), financial advisers (Ray Chamberlain), accountants (Scott Jeffery, Sam Hay, Brett Rosebury), a quality systems manager (Shane McInerney), cartographer, engineer, logistics planner –- even a rocket scientist (aerospace engineer Robert Findlay).
Analysing baseball officiating,
Sportcasting notes: “We can’t expect umpires to be perfect, and in fact they call strikes and balls correctly 85.6 per cent of the time. But the errors they do make don’t seem to be random. They favour the home team.”
What have other sports done about this?
An interestingly aspect of the psychology has been apparent in US baseball, where the NBA was so concerned about official bias that it installed technology at a number of grounds to analyse umpires’ calls.
When the referees were aware that their decisions were being closely scrutinised -– and why -– suddenly everything changed.
The long established ratio of strikes to balls in the home sides’ favour suddenly disappeared and in fact swung to the visiting teams in what appeared to be a tendency to be over cautious and to over-correct.
Hoewever, this points to a benefit in closely monitoring officials’ decisions -- as has occurred to a greater extent in AFL in recent years.
Sawers makes the point that the scrutiny of AFL umpires has never been greater.
“Over the last 12 years with the use of technology and the ability to view incidents from so many angles, our guys are more scrutinised,” he said.
“They know that everything they do is assessed.”
He added that the umpiring department would be interested in evaluating any new research.
In all sports, a percentage of umpiring calls will always remain disputable.
Of the 47 incidents in the referee study, none resulted in a unanimous decision by all 40 qualified referees.
The designers of the UK referees’ study make one salient point on the introduction of video referees -– as has occurred in sports like rugby league.
“Is more than one official necessary to help adjudicate contentious replays and, most importantly, should the officials judge from a soundproof booth, avoiding the influence of crowd noise?” the authors ask.
In other words, the third umpire with the benefit of video replay is not as impartial an authority as one might think and will not necessarily make better decisions than the on-field officials (something that Australian rubgy league has discovered).
Unless, of course, they turn down the crowd.
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