The effects of COVID-19 on football players

COVID-19 leads to a persistent productivity decline in a high-performance environment

What happens to people infected by COVID-19 once the initial disease has been overcome? Early research has reported continued symptoms for some, so-called “long COVID”. However, evidence on the long-term effects of the novel coronavirus has relied on self-reporting and only covers people noticing such symptoms.

A novel study by researchers at the Heinrich Heine University Duesseldorf and the University of Reading reveals a strongly persistent performance deterioration of -5.1% among professional football players who have been infected with COVID-19.

The study will be presented at the annual conference of the Royal Economic Society. The researchers – Kai Fischer, J. James Reade, and W. Benedikt Schmal – find that the effect does not appear only temporarily, but remains over the course of up to eight months after a return to the pitch.

Further findings include large differences across age groups: While young players aged less than 25 are not significantly affected at all, players older than 30 face a major decline in performance, of about 10%. The deterioration especially applies during matches with short rest breaks beforehand: While breaks of two weeks seem to enable players to return to their initial performance, matches in a weekly or shorter than weekly sequence lead to significant declines.

In more detail, the German-British research team investigates the male elite football leagues of Germany (Bundesliga) and Italy (Serie A). With meticulous information gathering, they can identify nearly all COVID-19 infections among the teams in these two leagues. This allows them to analyse a “natural experiment”, that separates the total group of 1,406 players into 233 infected players and a control group of the remaining players. Both leagues implemented rigorous testing schemes that avoid the common problem of a large “dark” figure of unrecorded COVID-19 infections.

To examine the effect of COVID-19, the researchers use a statistical method called difference-in-differences. They compare the outcomes of the infected and the uninfected players before and after infection with COVID-19. Applying this method, the researchers can isolate the causal effect of the novel coronavirus on productivity on the football pitch.

While the information on infections stems from various data sources, the authors use data from an official sports data provider to measure performance. The main variable is the number of passes, but the results are robust to many different measures, such as ball touches or ball possession. The researchers also investigate potential “spillover” effects, from infected players to the performance of their teammates. They find no evidence for this for slightly affected teams, but a significant deterioration for severely affected squads with many infected players.

The findings bear important implications. Were the declines in productivity to appear in other occupations that rely heavily on physical effort, such as construction or care work, COVID-19 might lower productivity among millions of workers in the labour force and could further increase the need for workers in these sectors.

“The Long Shadow of an Infection: COVID-19 and Performance at Work” is available as University of Reading Department of Economics Discussion Paper No. 2021-17.


Kai Fischer (Heinrich Heine University) – @kai__fischer, kfischer@dice.hhu.de

J. James Reade (University of Reading) – @jjreade

W. Benedikt Schmal (Heinrich Heine University) – @schmal_w

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