Football referees aren’t just wrong, they’re biased

Football penalties are often controversial and the first couple of days of the World Cup have already provided one dubious decision. Luckily for the referee’s personal safety it favoured the hosts, Brazil. But, according to Randal Olson’s fascinating analysis of penalty decisions, there may be more than luck involved:

70.6% of all penalty kicks were awarded to the Home team.


Similarly, if the Away team received the first penalty kick, then the Home team received the second penalty kick 92.5% of the time — an incredible display of referee bias.

Check out the whole post for all the details and a bunch more stats!

3 replies
  1. lalitha
    lalitha says:

    I think your approach is pretty good. Most bloggers won’t have anything as elaborate or systematic as I do.

    Sounds like you have something that works well within your personality and schedule. Perfecto!

  2. Vanilla_Thrilla
    Vanilla_Thrilla says:

    Apologies I haven’t read the paper but I wonder if the 70:30 split at least
    partially reflects the fact that home teams do better at home, and therefore are likely to be in the away team’s penalty box more often? The share of second penalties I would think provides stronger evidence of bias.

    As to the dubiousness of the penalty you mention I would disagree for the reasons outlined in this post:

    If you don’t want some poncy soccer player to flap around on the ground like a salmon, don’t grab his shoulder in front of the ref

    • jamesz
      jamesz says:

      Good point: we wouldn’t necessarily expect the penalties to be 50:50 if it were unbiased. It’s not actually a paper, just a blog post so you could even do some follow-up analysis yourself to check the expected distribution.

      Fair enough about the penalty. I only meant it has been contested; I didn’t intend to express a view about which way it should have fallen!

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