Corners are funny events; not funny as in "ha ha" but funny as in "what do they tell us about the game?".
Let's think of them as measures of offensive production for a moment. Teams playing lots of offense should not see too many corners on their own side of the field. Instead, teams that press, have lots of possession, pass forward a lot and take lots of shots on goals should, by implication, see some of the balls diverted by goalies or defenders to produce corners.
So corners should be correlated with shots on goal, right? And they, in fact, are - across the big leagues and the years. Take a look at this graph of the relationship between the number of corners in a match and the number of shots on goal for the 2005/06 to 2009/10 seasons.
The graph paints just the kind of picture you would expect. Yes, there are some variations across the leagues, but more shots are associated with more corners (and the other way around). The Pearson correlations range between .44 in La Liga to .51 in the Bundesliga. On average, teams that take 10 shots or fewer can expect to see 5 or fewer corners; teams that take about 15 shots get about 10 corners and so on. At the high end, the correlation peters out and becomes more variable.
So this should mean that teams that shoot more and get more corners also manage to score more goals, right? Wrong, it turns out. When we quantify the offensive "value" of corners, we find that corners do not have much of a goal value; in fact, across the leagues, goal totals do not increase with corner totals. The correlation is essentially 0 (it's strongest in the EPL at .06, and weakest in Serie A and La Liga at less than .01). Take a look at a graphical representation of this pattern, keeping in mind that the average number of goals a team scores per match is around 1.3 across leagues and seasons.
Turns out, knowing that a team has generated lots of corners does not improve your prediction of how many goals that team will score (in fact, as the number of corners increases, the goal totals become increasingly variable).
Surprising? Well, a little, but not if you consider how teams create corners. Oftentimes, teams are awarded a corner precisely because they did not manage to score (so perhaps the relationship should be negative). But in any case, balls that do not cross the goal line between the posts but next to them turn into corners.
PS: Mind you, these data cannot tell us the odds that any one corner yields a goal - they are simply match totals.
Let's think of them as measures of offensive production for a moment. Teams playing lots of offense should not see too many corners on their own side of the field. Instead, teams that press, have lots of possession, pass forward a lot and take lots of shots on goals should, by implication, see some of the balls diverted by goalies or defenders to produce corners.
So corners should be correlated with shots on goal, right? And they, in fact, are - across the big leagues and the years. Take a look at this graph of the relationship between the number of corners in a match and the number of shots on goal for the 2005/06 to 2009/10 seasons.
The graph paints just the kind of picture you would expect. Yes, there are some variations across the leagues, but more shots are associated with more corners (and the other way around). The Pearson correlations range between .44 in La Liga to .51 in the Bundesliga. On average, teams that take 10 shots or fewer can expect to see 5 or fewer corners; teams that take about 15 shots get about 10 corners and so on. At the high end, the correlation peters out and becomes more variable.
So this should mean that teams that shoot more and get more corners also manage to score more goals, right? Wrong, it turns out. When we quantify the offensive "value" of corners, we find that corners do not have much of a goal value; in fact, across the leagues, goal totals do not increase with corner totals. The correlation is essentially 0 (it's strongest in the EPL at .06, and weakest in Serie A and La Liga at less than .01). Take a look at a graphical representation of this pattern, keeping in mind that the average number of goals a team scores per match is around 1.3 across leagues and seasons.
Turns out, knowing that a team has generated lots of corners does not improve your prediction of how many goals that team will score (in fact, as the number of corners increases, the goal totals become increasingly variable).
Surprising? Well, a little, but not if you consider how teams create corners. Oftentimes, teams are awarded a corner precisely because they did not manage to score (so perhaps the relationship should be negative). But in any case, balls that do not cross the goal line between the posts but next to them turn into corners.
PS: Mind you, these data cannot tell us the odds that any one corner yields a goal - they are simply match totals.
