A few days ago, I took a look at the origins of goals in the first half of this year's Premier League season to see what we can learn about the connection between different match situations (defined as open play, corners, fast breaks, penalties, and free kicks) and goal creation.
In case you didn't have the time or inclination to read the details, here's the upshot: Keeping in mind that teams scored on average 1.35 goals per match, the overall distributions showed that a sizable majority of goals were created from open play at a rate of .9 per match. The remainder (about .45 per match, since 1.35-.9=.45 so right around almost half a goal) were generated from corners (.18), penalties (.095), fast breaks (.074), and free kicks (.038). The relative contributions of each kind of match situation to goal creation were as follows: roughly 70% of goals were scored from open play, 14% from corner situations*, around 7% from penalties, almost 6% from fast breaks, and the remaining 3% from free kicks.
These averages are interesting as far as they go. But knowing that 70% of all goals were created from open play situations does not necessarily tell you that shots from open play are more likely to produce goals. It simply means that teams spent more of their time and effort on creating goals from open play.
Because these numbers do not tell us anything about conversion or efficiency - that is, the combined odds that shots from different match situations will be accurate and converted to goals - below I calculated the goal creation ratios - goals to shots - from different match situations based on data from the Opta/Guardian Chalkboards. These numbers are shown below; they indicate the odds that shots from different match situations actually end up in goal.
The overall ratio for all goals and shots from all match situations (not shown in the graph) was .097; that's right around 1 goal in 10.25 shots. By far the most efficient shots - unsurprisingly - were penalty kicks with a ratio of .69. This translates into 1 goal for every 1.45 penalty shots taken. In stark contrast, the goal creation ratio for free kicks is a truly lousy .039. That's about 1 goal for every 25 shots from free kick situations. Another way to think about these numbers that the odds of scoring from a penalty are 18 times better than the odds of scoring from a free kick situation.
Clearly, penalties are unusual, and it's a little bit comparing apples and oranges comparing them to other match situations. So to get a cleaner comparison of "typical" match situations, below is the same graph but with the bar for penalties removed. Take a look.
In case you didn't have the time or inclination to read the details, here's the upshot: Keeping in mind that teams scored on average 1.35 goals per match, the overall distributions showed that a sizable majority of goals were created from open play at a rate of .9 per match. The remainder (about .45 per match, since 1.35-.9=.45 so right around almost half a goal) were generated from corners (.18), penalties (.095), fast breaks (.074), and free kicks (.038). The relative contributions of each kind of match situation to goal creation were as follows: roughly 70% of goals were scored from open play, 14% from corner situations*, around 7% from penalties, almost 6% from fast breaks, and the remaining 3% from free kicks.
These averages are interesting as far as they go. But knowing that 70% of all goals were created from open play situations does not necessarily tell you that shots from open play are more likely to produce goals. It simply means that teams spent more of their time and effort on creating goals from open play.
Because these numbers do not tell us anything about conversion or efficiency - that is, the combined odds that shots from different match situations will be accurate and converted to goals - below I calculated the goal creation ratios - goals to shots - from different match situations based on data from the Opta/Guardian Chalkboards. These numbers are shown below; they indicate the odds that shots from different match situations actually end up in goal.
The overall ratio for all goals and shots from all match situations (not shown in the graph) was .097; that's right around 1 goal in 10.25 shots. By far the most efficient shots - unsurprisingly - were penalty kicks with a ratio of .69. This translates into 1 goal for every 1.45 penalty shots taken. In stark contrast, the goal creation ratio for free kicks is a truly lousy .039. That's about 1 goal for every 25 shots from free kick situations. Another way to think about these numbers that the odds of scoring from a penalty are 18 times better than the odds of scoring from a free kick situation.
Clearly, penalties are unusual, and it's a little bit comparing apples and oranges comparing them to other match situations. So to get a cleaner comparison of "typical" match situations, below is the same graph but with the bar for penalties removed. Take a look.
Here, things become a bit clearer as far as efficiency is concerned. Leaving penalty kicks aside, by far the most efficient match situations are shots from fast breaks at a rate of about .14. This means that teams will score a goal from transition play at a rate of 1 to every 7.25 shots taken. That's about three and a half times as efficient as free kick situations. Corners and open play situations are in between at a rate around .9 (.088 and .09, to be exact). That's about 1 goal in every 11 shots or 34% less efficient than fast break situations. Here's another way to think about these numbers: to produce the same expected number of goals, you have to get 1.5 shots from corners or open play situations for every 1 shot from a fast break situation. And the relationship is even more lopsided vis-a-vis free kicks: teams have to produce 3.5 shots from free kicks to produce the same expected number of goals as they can generate from fast breaks.
What does it mean? I'll leave that to managers to sort out, but it does point to the verifiable futility of generating goals from free kicks, and the relative inefficiency of generating goals from corners and open play compared to goals from fast breaks. Before too long, I'll take a look at team differences in how they produced goals to see if there are significant differences in how teams managed to create goals this year.
What does it mean? I'll leave that to managers to sort out, but it does point to the verifiable futility of generating goals from free kicks, and the relative inefficiency of generating goals from corners and open play compared to goals from fast breaks. Before too long, I'll take a look at team differences in how they produced goals to see if there are significant differences in how teams managed to create goals this year.
* Though what does and does not count as a corner situation depends on how you define it, of course.
