Is There a World Cup "Group of Death"?
Much is made following the World Cup draw every four years over which group is the “group of death.” This is generally considered to be a really difficult group that is tough to advance from, although there is no true definition (more on that below).
First, for readers not familiar with World Cup groups, a brief explanation of how teams are “grouped” in the World Cup is in order. Thirty-two teams qualify to compete, and they are placed into eight different groups labeled A-H, with each having a predetermined “top” team. In the group stage of the World Cup, each team plays the other three teams in their group, and the top two teams move into a standard bracketed tournament. The bottom two teams watch the rest of the tournament on TV, like the rest of us.
So how do you decide which group is the Group of Death?
There is no formal definition, so let’s look at a few possibilities and see what we can learn by analyzing some data. To do so, I’m going to use the team ratings found at eloratings.net although other rating systems exist.
Highest Average Rating
One quick method to look for a Group of Death would be to see which group has the highest average rating among their four teams…this group would be the most difficult, after all.
Here are the ratings of every team in every group, with the group average plotted as well:
Group B (Spain, Netherlands, Chile, Australia) obviously has the highest average, followed by Group G (Germany, Portugal, USA, Ghana). So based on this method, Group B is the most difficult and the Group of Death for 2014.
But take a closer look at Group B, and you’ll notice how widely spread the teams are…the top team (Spain) is significantly better than average, and the bottom team (Australia) probably has little hope of qualifying. If the top team is likely to qualify and the bottom team likely is not, then the group really can’t be that competitive and considering it a “Group of Death” seems a bit dramatic.
What if instead we considered the Group of Death to be one in which the teams are closely rated, which makes the group highly competitive – even the best team is far from certain to advance past the group stage.
So instead, let’s look at the standard deviation of the ratings within each group:
Now we see that Group C (Colombia, Greece, Ivory Coast, Japan) is actually highly competitive and may qualify as the Group of Death.
2nd to 3rd Gap
It could be, however, that the entire group doesn’t need to be highly competitive in order to be a “Group of Death.” The Group of Death designation could simply mean that it is not clear which teams are most likely to advance. Having one really weak team in your group would raise the variation, but if the other three are very competitive with one another then your group could easily get the title.
First, let’s take a look at the rating difference between the second- and third-highest rated teams in each group:
By this measure, Groups A, D, and E look to be very competitive for making it to the second spot to advance.
Top 2 Versus Bottom 2
Another measure of competitiveness for advancing would be to look at the average ratings of the top two teams in each group versus the bottom two, as a large difference indicates that it is unlikely there will be surprises within the group:
By this measure, Groups C, D, and E appear highly competitive and the bottom teams can easily surprise and move on, making it a Group of Death for teams rated at the top.
Best Team Left Out
As a final measure, I’ll look at the highest-rated team left out after the group stage. The third-highest rated team in any group has the lowest possible rating of the best team left out. So the better that team is, the better the group fits the Group of Death mold: a very good team will not move on because of the difficulty of the group.
Here is the rating of the third-best team in each group:
Groups B and D each have really good teams that are only the third-best in the group, meaning at least one really good team will not advance from these groups. In fact, the third-best teams in these groups rank 10th (Chile) and 11th (Italy) in the world! By comparison, the third-best team in Group H is ranked 42nd (South Korea) in the world.
So Which Group Is the Group of Death?
The analysis here definitely illustrates one thing: without any agreed-upon definition of a “Group of Death,” it is very difficult to clearly distinguish which group deserves the designation.
Sometimes there is no single metric that best measures what you’re trying to analyze, and looking at a few different measure helps clarify things. Although not the most extreme on many of these methods, I would look at Groups B and G as the most likely candidates for Group of Death in 2014 World Cup, as each tended to rate well on most measures.
That is, unless there isn’t really such a thing as a Group of Death…