Sunday, July 13, 2014

World Cup Wrap Up: Goal Differential

Before the beginning of the World Cup, I modeled expected goal differentials for every team. As the World Cup comes to an end I thought it would be fun to look at what the model expected from teams vs. what they did.

Goal differential is Goals Scored minus Goals Conceded. Let's take the USA#1 as an example:

USA scored 2 goals against Ghana and allowed 1, so for that game they had a goal differential of 1. For the tournament as a whole the USA scored 5 goals and conceded 6 for an overall goal differential of -1. Make sense?

For the whole tournament, the model predicted the USA would have a goal differential of -2.5. By coming in at -1, the USA out performed the model's expectations by 1.5 goals (WOOHOO USA#! etc).

How did the rest of the field do?

  • Netherlands and Germany have both been over 8 goals better than the model expected (and Germany still has one game to go)!
  • Some of the fun positive surprises (Costa Rica, Mexico) jump out at the top of the list, and of course the wild disappointments (Spain, Portugal) sit near the bottom
  • Brazil being in last is a function of them having a very high positive expected goal differential and (of course) them having given up 10 goals in their final two games
  • This isn't an absolute ranking of teams, but a ranking of how teams have performed relative to expectations

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