New research at the School has found that a score-dependent alternating order in penalty shootouts is fairer than the order currently in use.

It has long been debated whether the traditional ABAB system, where players from opposing teams take it turns to take their penalties, was the fairest and most unbiased way to order shootouts. There has also been the ABBA system, where the order of turns is mixed, which has recently been introduced into the English EFL Cup.

Previous studies have suggested that the team shooting first in an ABAB system is much more likely to win. However, in an ABBA system, though the first shooting team is also more likely to win, the odds are reduced.

#### A new proposed method

In a new study, Nejat Anbarci, Professor of Economics at the School, together with colleagues from Deakin University and Boston College, Professors CJ Sun and Utku Unver, was keen to test a new method of penalty shootouts against both the ABAB and ABBA system.

One variant of the new method allowed for completely random ordering between both teams for the initial five penalties, and also in the event of sudden death scenarios. In another variant of the new method, the team which is behind at the end of a round (each set of two penalties) goes first in the next round. This makes it a score-dependent method.

#### How the proposed score-dependent method was tested

The authors created a which theoretically simulated the penalty kicks in all three types of penalty structure in order to conclude which of the methods was the fairest and most equal.

The study found that:

• their proposed ‘score-dependent alternate order’ penalty shootout was both fair and equal in both regular penalties and sudden death
• the ABBA system was only fair and equal in sudden death
• the ABAB system was not fair or equal in either.

“Economists have long recognised the effect that the order of actions in sequential contests can have on performance. Penalty shootouts in football offer a very clear and real-life example of this, showcasing whether the order effects the probability that a specific team is likely win.

“Our research showcases the best possible structure for penalty shootouts, in order to make them as fair and equal as possible, therefore ensuring no team in a shootout has an unfair advantage over the other.” Professor Nejat Anbarci

#### Making it into a reality

Though the findings have proven a score-dependent alternate ordering may be the fairest and most equal way in which to conduct a penalty shootout, the authors understand the difficulties around implementing this type of structure into an actual penalty shootout, no matter how equal it would be.

To that end, they hope to conduct major field studies to compare their score-dependent alternate order penalty shootout face-to-face with ABAB and ABBA which may open the door to the widespread use of their shootout system in major football championships in the future.