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The Football Match, LS Lowry, 1949

From London Review of Books:

Until recently, one of the most remarkable unbeaten records in sport belonged to a football manager, the much reviled Portuguese provocateur and clotheshorse José Mourinho. Before Real Madrid lost 1-0 at home to Sporting Gijón on 2 April, no team managed by Mourinho had lost a home league game for more than nine years, a sequence spanning four different clubs in four different countries (Mourinho has also managed Porto, Chelsea and Inter Milan) and lasting 150 matches. It is true that Porto, Chelsea, Inter and Real are all rich and powerful clubs and you would not expect them to lose at home very often – but still, nine years is a mighty long time. Even if you calculate that on average away teams only ever had a 10 per cent chance of beating one of Mourinho’s sides (for some, like Gijón, it might be a lot less, but for others, like Sporting Lisbon, AC Milan, Manchester United or Barcelona, it would be a lot more), the odds against going unbeaten for 150 matches are more than seven million to one.

How did he do it? The difficulty in answering this question is that there are really two puzzles here. The first is Mourinho. Is he supremely talented, or supremely lucky, or a bit of both? Does he have a secret formula, or is the secret that there is no formula, just enough bravado to make it look like he knows what he is doing? But the other puzzle has nothing to do with Mourinho. It is the mystery of home advantage itself. Why is it so hard to beat a team in its own stadium? Why does every team, no matter how unbeatable at home, lose something of its invincibility when playing away? Chelsea, who did not suffer a single home defeat during Mourinho’s three and a bit years in charge, were beaten ten times away from Stamford Bridge during the same period. If you calculate that the chances of beating one of Mourinho’s teams rise to about 20 per cent when they play away from home, then the odds of his going unbeaten for 150 away matches are nearly 350 trillion to one. It’s never going to happen to him or to anyone else.

It’s not only the big clubs. Take any European football league in which all the teams play each other twice in a season, once at home and once away. Add up the total number of home victories and compare it to the total number of away victories. The ratio will be at least 60:40 in favour of the home sides (often it’s more: in the English Premier League home advantage currently runs at around 63 per cent, in Spain’s La Liga it’s 65 and Italy’s Serie A it’s 67). The advantage holds across almost every major sport, though exactly how big it is tends to vary. Fans are so used to this that they take it for granted their team is much more likely to win on its own turf. They also take it for granted that they know why – it’s because the home crowd is cheering the team on. But there is no evidence for this. In fact, despite a fair amount of research in the top sports science journals, there is no conclusive explanation of what makes teams play better at home. This is the real puzzle about home advantage: everyone knows it exists but no one knows why.

“Swing for the Fences”, David Runciman, London Review of Books