The Removal of the Away Goals Rule: Intended or Unintended Consequences?

Prior literature offers many examples of rule changes in sport which failed to achieve their objectives or even had perverse consequences. Here, we study a rule change in football competitions organised by UEFA, which removed the away goals rule used as a tie-breaker in two-legged fixtures. The analysis is based on 1,100 ties played before the reform and 752 after. We find that, largely, the change was successful in achieving its stated objective of increasing scoring-rates by teams playing in their own stadium, and it removed any disadvantage from being drawn to play the first match at home. Penalty shoot-outs to settle the issue of which club would proceed further in the competition became much more common. All these effects were, however, confined to particular ranges of the strength difference between the two clubs. The reform appears to have favoured stronger clubs, with a reduction in the incidence of upsets.