Fitness, chance, and myths: an objective view on soccer results

TL;DR

This paper uses a model-free analysis of Bundesliga data to challenge common beliefs about soccer results, showing goal difference as a better fitness measure and revealing insights into team performance dynamics and myths.

Contribution

It introduces a novel framework for statistically characterizing soccer results and provides new insights into team fitness, streaks, and home advantage using data-driven methods.

Findings

Goal difference is a better fitness measure than points.

Team fitness varies mainly during the summer break.

No statistically significant team-specific home advantage.

Abstract

We analyze the time series of soccer matches in a model-free way using data for the German soccer league (Bundesliga). We argue that the goal difference is a better measure for the overall fitness of a team than the number of points. It is shown that the time evolution of the table during a season can be interpreted as a random walk with an underlying constant drift. Variations of the overall fitness mainly occur during the summer break but not during a season. The fitness correlation shows a long-time decay on the scale of a quarter century. Some typical soccer myths are analyzed in detail. It is shown that losing but no winning streaks exist. For this analysis ideas from multidimensional NMR experiments have been borrowed. Furthermore, beyond the general home advantage there is no statistically relevant indication of a team-specific home fitness. Based on these insights a framework for a statistical characterization of the results of a soccer league is introduced and some general consequences for the prediction of soccer results are formulated.