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What is a corner kick worth in soccer?

(Photo by Laurence Griffiths/Getty Images)

Last night, the United States won a corner in the 86th minute. The Americans had attempted all of two shots in the preceding 40 minutes of play, but this one chance was all they would need. Graham Zusi struck a near-perfect delivery from the corner flag, John Brooks got free and kept his header down, and it was pandemonium through the nation.

How likely was this outcome? When a soccer team wins a corner or a free kick, how likely is it that they’re about to score? For the United States it took just two corners in the second half to score a goal. For the average side in club soccer, it takes closer to 30 corners for a goal.

In the English Premier League since 2011, there have been over 12,000 corners taken. A small percentage of these corners have been taken short, but on the vast majority (over 10,000) a cross into the box was attempted. This forms a solid sample for analysis.

(A similar study on this topic was performed by Chris Anderson and David Sally of Soccer by the Numbers. This post extends the analysis and brings to bear a larger sample of data.)

Zusi and Brooks demonstrated the simplest way to cash in a corner. Strike a good cross, make a good run, get your head to the ball and start celebrating. But overall, this does not happen very often.

Out of 10,969 crosses from the corner, the vast majority did not even produce a shot. They went long, got cleared, or caromed around the penalty area before going out of play harmlessly. Only 12 percent of these corners produced a legitimate shot attempt. Simply getting a shot away from a corner kick is an accomplishment. Of the 1,362 shots directly assisted by corners, 182 were knocked home for goals. So that’s a scoring rate of about 13 percent for shots assisted by corner kicks. And an overall rate of goals scored from corner kicks of a little less than 2 percent.

Now, this is not the only way to score from a corner. Most obviously, a goal can be scored after a flick-on, a slight touch to redirect the corner kick such as the one by Abel Aguilar that set up Teofilo Gutierrez for Colombia’s second goal against Greece. There can also be the goal mouth scramble, or the short corner which leads quickly to a good chance. Opta classifies these chances as following “a corner kick situation,” and they show the value of a corner kick to be slightly higher than the 2percent cited above.

From 12,750 corner situations, eventually teams produced 2,157 shots. So the creation of shots is a little more likely, up to 17 percent of corner kicks lead to shot attempts. These shots are scored at a somewhat higher rate, as well. I have 370 goals from corner kick situations, for a scoring rate of 17 percent. It makes sense that these shots from corner kick situations should be converted at higher rates. Shots taken with the head or assisted by a cross have conversion rates 25 to 50 percent lower than other shots attempted from the same locations. Shots directly assisted by corners are by definition assisted by crosses, and the majority will be headers. These are a low-value set of shots. The struggles of Ghana to convert their chances last night are directly correlated to how many of those shots were headers of crosses. By contrast, shots following from corner situations will include higher expectation chances like Gutierrez’s.

Overall, corner kicks lead to goals about 3 percent of the time. A header like Brooks’s dramatic winner occurs roughly every thirty tries. This does not mean that the Americans were lucky to score. Zusi’s delivery was impeccable, and Brooks’s run and jump very good. But the problem is, it’s incredibly difficult to deliver a perfect corner. This season in MLS, Graham Zusi has taken 41 corners, only seven of which have assisted shots, and not one has scored. Even a dead ball specialist like Zusi usually cannot find his teammate’s head for a perfect chance. So while the goal itself was a product of skill, we cannot expect a corner kick to provide a goal with any regularity. If the United States is to take needed points against Germany and Portugal, it will most likely require good chances created through the center in open play.

All data provided by Opta unless otherwise noted.

Michael Caley writes for Cartilage Free Captain, where he analyzes fancy soccer statistics and bemoans Tottenham Hotspur’s most recent failures. You can follow him on twitter at @MC_of_AMy full World Cup projections and methodology can be found at SB Nation.