A Research on the Relative Age Effect in Football

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The purpose of the study was to investigate the performance level at which birth date effects selection for performance pathways in English football, as well as examining whether coaches are currently implementing arrangements to limit the relative age effect. The study comprised of 2450 players from performance levels including community, grass root and academy. The birth dates of each player within every performance level were analysed through the use of statistical tools within Microsoft Excel, with interviews analysed through transcription and the highlighting of recurrent themes. The sub-groups were viewed by age group, month of birth and the total percentage of players born within each quartile of the selection year to analyse the birth bias within specific performance levels. The statistical data of each sub-group were then collated to view differences in progressing through each performance level.

The main results found an over-representation of players born in the first quartile throughout each performance level. The bias within the community and grass root subgroup was 4.1%, with a 39.9% bias towards the eldest players at academy standard. The evidence highlighted that birth date only has significant impact on selection once the academy standard of play is reached, with minimal difference in impact when progressing through inferior performance levels. Coaches in the study showed high awareness of the effect, with implementation of two strategies to reduce the relative age effect being implemented. The two strategies were found to be ineffective in the reduction of the relative age effect, through implementation occurring after selection.

To conclude the academy pathway highlighted the most significant bias, with birth date having minimal impact at inferior performance levels. Strategies to reduce the relative age effect are currently ineffective requiring further research into reducing the bias prior to selection.



  • To investigate the performance level at which birth date may affect selection for performance pathways in English football.
  • To examine if football coaches are making arrangements to limit the Relative age effect in football

Research Question

In English football is there a starting point to the relative age effect and if this is the case then how are football coaches currently taking this bias into consideration when working with children at all levels of football.  


Relative age effect is the difference in ages between children in the same age group. An example being, a child born in the start of the selection period in football i.e. 1st September will be 11 months older than a player who falls in the same age group born on the 1st of August. (Barnsley et al, 1992) Throughout the study research has referred to the relative age effect as birth date and birth bias, all meaning the same.

The football world is competitive and making sure that your team are developing young athletes to progress into the first team and national team is very important. This has made the selection and development of children an important aspect in youth football.

Studies have progressively shown that in football there are children not given the opportunity, due to a simple aspect such as their age. (Brewer et al 1995; Cobley et al 2008; Delorme et al 2010) The research that has previously been carried out has rarely been specified around the English game with only a minority being carried out in this area. (Simmons & Paull, 2001; Musch & Grondin, 2001) The research has predominantly been aimed towards a number of different nations across the world. (Glamser & Vincent, 2004; Jimenez, 2008; Delorme et al 2010; Campo et al 2010) The limited amount of research on the English game highlighted an area in which further study could be carried out in order to fully understand the impact the relative age effect has within English football. Correspondingly the research into the affect performance level has on the impact of the relative age effect within English football has been under-represented by preceding research. The research specific to this area often views different nations or sports. (Mujika et al, 2007; Cobley et al, 2009; Till et al, 2010) The knowledge of how performance level could affect selection will allow understanding of where birth bias is present and predominant, furthermore highlighting the level at which change is needed to reduce the relative age effect. The results will be of great value to coaches within the performance level that the relative age effect is most predominant by raising awareness and creating knowledge for change.

Preceding research has also viewed how different organisations and football associations have tried to reduce the impact of the relative age effect in different countries. (Helson et al 2000; Vaeyens et al 2003) Although this research has shown how interventions have been made there has not been a study on how the coaches within the football clubs in these associations are practically trying to reduce the bias or in fact if they are. This is an area of research that is being analysed. The Qatar World Cup 2022 starting line-ups for many of the world’s top teams show there is still some distance to go to truly combat age related bias, with the average player age for a squad being just 23. (Andrews et al, 2022) This will help compare the current tools being put in place and to see if there is a working intervention to help reduce the birth bias. The context of the study will include raising awareness of the relative age effect to the coaches in which the relative age effect is most predominant within the standard at which they coach. Research has previously highlighted this to be an advantage in reducing the effect, increasing the value of the study. (Baker et al, 2010; Cobley et al, 2009)  

The study begins viewing previous research on the relative age effect reviewing specifically topics around the aims and secondary topics in which can affect the predominance of the effect. The second section views the method in which the study carried out the research with reasoning and description, progressing onto the results in which are presented with the discussion following. A conclusion in relation to the aims of the study is carried out in the penultimate section, ending with self reflection discussing the learning throughout the study.   


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