Home advantage is a well-established feature of football, and researchers have identified many and varied causes, ranging from crowd effects, familiarity with the home stadium, travel fatigue, and even increased testosterone levels.
There can be little doubt that teams do play better - and differently - at home. For example, I looked at a broad sample of over 27,000 first-tier matches from around the world. Teams playing at home make 8% more passes overall but 19% more final-third passes than teams playing away. In other words, home teams have more possession than away teams, and are more likely to attack when they do have possession , (Just the kind of aggression you’d expect from a testosterone fuelled bunch of lads in fact!)
But it’s interesting to look at the more specific case of penalties. Here the game shrinks to a one-on-one, test of nerves and the psychological pressure is intense. How does home advantage play out in this scenario?
Performing effectively under the pressure of expectation is quite a stressful task, and from this perspective the goalkeeper and penalty-taker see things quite differently. The goalkeeper has nothing to lose, and everything to gain. But for the penalty taker it’s just the opposite. I’m sure we all remember occasions when even the seemingly strongest characters have buckled under the task and ballooned the ball over the bar or shot tamely into the keeper’s welcoming arms.
But both the away team penalty taker and the away team goalkeeper face the same hazard; a barrage of noise from the home crowd trying to put him off. How does that affect the results?
The answer is - perhaps surprisingly - not very much at all. Although home teams are awarded vastly more penalties than away teams ( 66% more in my sample), the scoring rates home and away are much of a muchness; 77.3% for home teams and 75.0% for away teams. The difference is statistically significant, but its not earth-shatteringly large. Scoring 2% more penalties is not going to turn anyones’s season round.
So where does the difference come from? Well if we look at off-target penalties, there is almost no difference. 6.3% off-target at home against 6.5% off-target away. The difference is that more on-target penalties are saved by the home team goalkeeper(11.8%) than the away team goalkeeper (10.1%). One possibility is that away-team penalty-takers behave differently. Perhaps they fear missing the goal and are less likely to shoot close to the posts. That would make penalties easier to save. Well, it’s a nice theory, but it isn’t supported by the facts. Whether at home or away, the coordinates of the ball as it crosses the goal line are pretty much the same, as the charts below make clear. (The away curves are scaled up to make them easier to compare with the home curves)
In both cases, the home and away ball-placements are statistically indistinguishable.
So we are left with two alternatives. One is that goalkeepers are slightly worse at saving penalties away; the other is that away penalty-takers are slightly worse at taking them. Perhaps they hold back slightly, and though they place the ball in their preferred position, it’s a little less firmly struck, enabling the goalkeeper to do slightly better.
But in either case, the practical effects are quite small. It seems that both goalkeepers and penalty-takers have sufficient mental resilience to prevent the away crowd interfering with their performance.