Thomas Dohmen, of the University of Bonn, has just published a study of the behaviour of German referees in 3500 matches in the 12 years to 2004. He finds that statistically they are biased in favour of whatever team happens to be playing at home. They lengthen those games in which the home team is behind and they award it more disputed and incorrect penalties than they do its opponents.
But not for the reason you might think.
What is important, Thomas finds, is not the referee's own affiliation, but unrelated factors such as the composition of the crowd, the stadium's design and the spectators' proximity to the field. Of particular importance is whether or not the match takes place in a stadium with a running track.
With a running track spectators are kept at bay and the referee is more likely to make correct decisions. Without one, referees seem to succumb to crowd pressure. As he puts it: "Referees are 10 per cent less likely to decide correctly when the game takes place in a stadium without a track."
Dohmen is not the first economist to discover that although referees are paid to be objective, their decisions are affected by the mood of the crowd around them...
In 2002 British researchers played to professional referees videotapes of an English Premier League game and asked them to decide whether or not to award a foul. One group watched the tape in silence. The other heard the crowd noise. The group that was able to hear the crowd awarded 15 per cent fewer fouls against the home side.
These economists aren't studying football for its own sake. They are examining it because it is one of the best ways of working out how we make decisions in the rest of our lives.
Do supervisors in our workplaces bend their assessments of their employees in the face of social pressure from the people around them? It is very hard to tell. But for football, where there is plenty of data, it is easy.
And as many of us who've just watched the penalty shoot-outs in the World Cup can attest, it can also tell us about our preparedness to take risks.
The economist Steven Levitt and colleagues from Stanford University and the University of Chicago have examined the direction in which players kick when they are offered a penalty.
They find that they kick the ball straight down the middle much less often than they should if their aim was to maximise the chance of getting a goal. Why choose the more risky route or kicking to the right or the left rather than going straight down the middle?
As Levitt puts it: "If you kick it right down the middle and you don't score, it is damn embarrassing. So even though the middle is a great play statistically, kickers don't choose it very often. There are some things that are even more important than winning, like not looking like a fool."
It is an extraordinary finding, because in professional sport decisions are meant to be about results, not feelings. The players are paid incredibly well, their every move is documented and an awful lot depends on the outcome. And yet they are prepared to compromise it in order to avoid being embarrassed.
It is common in US baseball as well. Three years ago Michael Lewis published Moneyball, described in some reviews as the best book about sport ever written. In it he documents the rise of the California's Oakland As, one of the poorest teams in the league. Instead of choosing its players on the basis of gut feel (where the decisions of its scouts might succumb to social or peer pressure) it used a laptop and cold hard stats.
The players it chose were more likely to take risks that might make them look foolish. Because of that they did better.
But they looked appalling. Most looked nothing like the jocks chosen by the teams with big money. They were lanky, fat, old or slow. And cheap, with few inhibitions.
It was a strategy that enabled the Oakland As, the league's second-poorest team, to win more regular season games than any other, with the exception of the Atlanta Braves.
Moneyball only appears to be a book about sport. It is actually a book about business. At one point Lewis asks: if professional sporting managers get so much so spectacularly and expensively wrong in a field in which there are clearly defined rules and massive documentation, what does that say about other fields, such as fund management, in which there are few rules and almost no documentation of minute-by-minute decisions?
Might the lowly paid administrators of non-profit industry funds do better than the big boys running the professional for-profit funds whose reputations are at stake? Might what applies to the business of sport apply to business more generally? The bigger your reputation, and the more you know you are being watched, the worse will be your decisions.
In those circumstances, might the best way to make decisions be as an ugly misfit, as were the players for the Oakland As. Or might it be to "turn down the sound" as did the referees in Britain?
Or, in the words of the country music ballad, to "dance like there's nobody watching, sing like there's nobody listening, and love like you'll never be hurt".
