Having analysed the statistics of players in the German Bundesliga, researchers from the HSE University Laboratory of Sports Studies found that the impact of defensive actions by players during a football match is much greater than contribution of such actions to their market value. The results of the study were published in the journal Applied Economics.
The phenomenon of market inefficiency, known as the Moneyball effect, was first introduced to analyse the value of baseball players in the United States. Billy Beane, manager of the Oakland Athletics team, tried to determine the characteristics and skills of players that increase the chances of winning, but were underrated by the market.
HSE Laboratory of Sports Studies researchers Inna Zaitseva and Daniil Shaposhnikov studied how this phenomenon works in the football market. It turned out that football defenders are underrated by the market compared to attackers. They receive lower salaries on average and get prestigious awards (such as the Golden Ball) less often, since their defensive efforts are more difficult to observe than spectacular attacking actions.
A successful attack becomes a spectacular event with a specific result—a scored goal, while successful defence ends with a goal prevented. The market might ignore the value of the players' efforts in defence, since the unscored goal is less spectacular.
However, football rules state that both scored and unscored goals are equally important for victory. Therefore, larger payment in favour of attacking players contradicts the principle of efficiency from the point of view of the economic theory of marginal productivity, when all factors of production are paid according to their contribution to the overall result. In this case, the efficiency of the team's expenses can be increased by reallocating the budget.
To check whether the real situation in football corresponds to the principle of efficiency, the researchers examined two sets of data from the German Bundesliga for the 2017/18 and 2018/19 seasons (1,224 and 772 observations at the level of teams and players, respectively).
The researchers created two models. One of them estimates the contribution of defensive and attacking actions to the success of the team, and the other estimates the contribution of defensive and attacking actions to the players’ market value. The distance that the players run, their age, the number of passes, the number of fouls, the positions of the players, the number of appearances on the field per season, and individual fixed effects were used as control variables in the study.
The results of the analysis showed an imbalance in the assessment of defensive and attacking efforts. It turned out that the contribution of defensive actions to the team’s victory is 75% greater than the contribution of the same actions to the market value of the players.
Defenders are underrated by the market, which reduces the efficiency of the team's budget allocation. Researchers believe that increased funding of defenders will help to raise this efficiency.
The Moneyball phenomenon is actively studied not only in sports; it applies to the entire labour market and is considered as part of the study of its inefficiency—for example, in medicine and law.