Dries Goossens is assistant professor at the Faculty of Economics and Business Administration of Ghent University. His research interests are mainly in tournament scheduling and related fairness issues (e.g. the carry-over effect); favorite sports are cycling and football (soccer). Together with Frits Spieksma, he has been computing the official schedule for the Belgian Pro League since 2006. Apart from sports, Dries Goossens has also done research on combinatorial optimization problems, such as combinatorial auctions, the transportation problem, and the assignment problem.
Fairness issues in sport scheduling: the carry-over effect
In 1847, Reverend T. Kirkman published the so-called “circle method”, which can be used for constructing a schedule for round-robin competitions. This method has been used abundantly in practice for many sports leagues around the world to construct schedules in round robin competitions. Consider the following phenomenon, which is relevant in any round-robin tournament. Imagine that your team is facing some other team in an upcoming match; we argue that the opponent of this other team in the previous match is relevant for your team’s upcoming match. Indeed, if the team you're about to face has experienced a heavy loss in its previous match, the team may have a low morale, or be discouraged, and hence perhaps easier to beat. Then your team is receiving a so-called carry-over effect from the previous opponent of the team your team is about to face. Of course, the opposite is possible as well: strengthened by having beaten a weak opponent in their previous match, the team your team is about to face is full of morale, and perhaps more difficult to beat. Obviously, any schedule includes carry-over effects, however, ideally these carry-over effects are balanced over the teams. In this talk we show that the circle method is the most unfair method with respect to balancing carry-over effects. Furthermore, we discuss a number of other fairness issues that arose when scheduling the highest division of the Belgian soccer league.