A Network Approach to the Transfer Market of European Football Leagues

Published in New Physics: Sae Mulli, 2015

Recommended citation: S. Lee, I. Hong and W.-S. Jung, "A network approach to the transfer market of European football leagues", New Physics: Sae Mulli 65, 402-409 (2015). http://www.npsm-kps.org/journal/view.html?uid=5214&vmd=Full

The transfer market for sport players presents an interesting issue both for the people who are directly involved with it and for the many fans. Although attempts have been made to understand it from a perspective of economy and management, an analysis from the view point of a complex system remains in the initial stages. In this research, we analyzed the transfer market of European football leagues as a weighted network in order to understand the detailed transfer patterns. A Google-based standard is used to quantify the value of the 436 transfers that occurred in the summer of 2014. The transfer patterns on a scale of both individual teams and whole leagues validate common sense intuitions about the capitalistic English Premier League. The log-normal distributions for players and teams imply that the network has evolved according to the Yule process. The properties of the network, such as assortativity, strength correlation, and betweenness centrality, provide several significant implications for topology. An assortativity coefficient close to zero represents a randomly-mixed transfer pattern on the league scale, which contradicts the intuitive assumption of disassortativity.