Il calciomercato: analisi di rete e equilibrio competitivo in 10 campionati europei

Football is one of the most popular sports in the world and it has consid- erably changed over the last thirty years. The aim of this thesis is to use data collected from the Transfermarkt portal to provide some insights into how the players’ transfer market and the balance of the competition within leagues have evolved. This is done by analyzing data from 10 European football leagues between the 1992/93 and 2021/22 seasons, which includes both information about football players and their transfers as well as information about the teams and their performance. The first point is investigated by constructing temporal directed weighted networks representing the transfers of players — both at a country and at a club level. Descriptive complex network analyses are carried out and the presence of actors, i.e. countries or clubs depending on the context, of particular importance within the structure of the networks is investigated through the use of algorithms such as PageRank and hyperlink-induced topic search (HITS). A comparison with a null model, obtained by con- sidering random networks built by using the configuration model, is also provided. In order to study the state of the competition within each league and its evolution, a few different indices based on sporting performance are defined to quantify how well-balanced a championship is and a correlation anal- ysis is performed to search for a relationship between the aforementioned indices and time. Furthermore, the wealth inequality among clubs within each league is measured by computing the Gini index, constructed by con- sidering the total player value of each club (available from 2004 onwards) as an indicator of club wealth. The Gini index is used to investigate the exis- tence of a link between wealth inequality among teams across time. Finally, the correlation between competitive balance and wealth disparity between teams within each league is investigated.