Monday, December 6, 2010

Corner Kicks… By the Numbers

Teams spend countless hours training for set pieces, both defending and attacking. This is because set pieces offer a valuable opportunity to score a goal. Of these, corner kicks provide an uncontested opportunity for the attacking team to play the ball across the goal and to execute a close range shot. A goal scored this way can quickly change the course of a match. But, how difficult is it to score a goal from a corner kick? How many goals are actually scored this way? Surprisingly, there is not a lot of solid research on these questions. A few scattered reports give varying numbers on how many corner kicks are attempted for each goal scored. Given this, the SSO decided to do its own analysis of corner kicks and goals scored. An in-depth look at the 2010 World Cup finals and 2010 Atlantic Coast Conference college season shed some insight on how many times a corner kick finds its way into the back of the net.

The first step was to analyze data provided on the FIFA World Cup website. They provide videos of all goals scored as well as statistics on the number of corner kicks attempted. There were 145 goals scored in the World Cup. Of the 627 corner kicks that were attempted, 271 connected with an offensive player (43%). Of those, 9 goals were scored from a corner played into the penalty area resulting in a shot. That’s a ratio of 1 goal scored for every 70 corners taken. Part of the difficulty with this analysis is defining how a goal is scored from a corner kick. Many consider more than one pass beyond the corner kick as free play. Others consider any goal scored where the run of play was initiated with a corner to have resulted from the corner. For example, a poor clearance by a defender that results in a successful shot could be attributed to the corner kick. Likewise a short corner that is touched a few times then played into the box and headed in might also be considered. If you also count goals that resulted from poor clearances (5) and from short corners (2), a total of 14 goals resulted from corner kicks. This brings the ratio down to 1 goal for every 45 corners attempted.

Using this approach, corner kicks accounted for as few as 6% or many as 10% of the goals scored during the 2010 World Cup and corner kicks resulted in a goal once every 4.5 to 7 matches.

The next step was to analyze goals scored and corner kicks attempted during US College matches. There were 36 matches played in 2010 season between men’s Atlantic Coast Conference teams. During this season, 104 goals were scored and 377 corner kicks were attempted. Of the goals scores, 5 were scored from the corner – a ratio of 1 goal per 75 corners attempted. An additional 4 were scored as a result of poor clearances, brining the ratio to 1 goal for every 42 attempts. As a result, a corner kicks accounted for 5-9% of all goals scored and a corner kick goal was scored once every 4-7 matches.

The reason for looking at the college matches was the assumption that it is more difficult to score against higher level defending. Thus, the number of goals scored per corner kick attempted should be lower for the World Cup matches. This is the case for the total number of goals scored per match. Slightly fewer were scored in the World Cup – 2.9 versus 2.3. However, the success rate for scoring goals from a corner kick was remarkably similar between the collegians and World Cup teams – one goal of every 70-75 or 40-45 attempts, depending on how the results are analyzed.

Two previous studies provide corner kick data. A random sample of English Premier League matches found that a goal was scored once every 36 corner kicks (Taylor et al, 2005). This study also reported that of 217 corners attempted only 31% resulted in a shot. A study of the Euro 2008 tournament (31 matches) showed that 313 corner kicks resulted in 26 shots (8%) and 5 goals – a 1:63 goals to corner ratio (Dunn, 2009). No information the origin of the goals scored was provided so we assume that they were from a corner kick shot into the goal.  Note added Jan 28: Lee Dunn confirmed that all of the goals scored at the Euro 2008 were, in fact, scored by the attacking player making first contact with the ball. Thus his ratio of 1:63 is very close to 1:75 value for the World Cup.

So, how difficult is it to score by a corner kick? These results suggest that it is quite difficult although this depends, in part, on how a goal from a corner kick is defined. The range is anywhere from 1 goal for every 36 to 70 corners attempted. Or, slightly less than 2% of corner kicks result in a goal. However, the same might be said for other goal scoring opportunities. Relatively few goals are scored by other means. Unlike basketball where more than 50% of attempted shots may result in a goal, only 8% of the World Cup shots found the back of the net. The problem is goals are difficult to score period. Given this, it is important for teams to take advantage of every opportunity, not matter what the odds. The lone goal in Spain’s 1-0 semifinal win over Germany was scored from a corner kick headed past the keeper. Clearly, this was an offensive opportunity that changed the outcome of the match. So, while it may be difficult to score off of a corner kick, they remain a critically important part of the game.

References:

Taylor JB, James N, Mellalien SD (2005) Notational analysis of corner kicks in English Premier League soccer. In: Science and Football V: the Proceedings of the Fifth World Congress on Football. T Reilly, D Aranjo & J Cabri (eds), pp 229-234.

Dunn L (2009) A Quantitative Analysis of Corner Kicks During UEFA Euro 2008, Austria & Switzerland, from www.thevideoanalysist.com, http://www.thevideoanalyst.com/pdf/cornerkicks.pdf. Downloaded, 26 November 2010.

Acknowledgement:

A word of thanks to Dr. Don Kirkendall for striking up the conversation about corner kicks and goals scored. Some of the most interesting conversations take place while watching a youth tournament!