The Relative Age Effect (RAE) is the term used to describe potential advantages or disadvantages that result from differences in age among children in the same cohort. We hear a lot about the Relative Age Effect in football (see the box below for an overview) but less often about RAE in female football specifically. As with many aspects of sport science research, there is often a lack of female representation in data sets (for example only 13 out of 115 articles on ‘soccer match demands’ included females as part of their sample (Emmonds et al., 2019). In one of the largest gatherings of RAE studies, spanning over 20 years of research, only 2% of the sample was female (Cobley et al., 2009). Given the known biological (and other!) differences between the sexes, the application of evidence derived from male athletes is a concern. This blog dives into what is known about the Relative Age Effect in female footballers.

RAE general overview

The relative age effect (RAE) refers to a preference for selecting athletes born earlier in the age-band due to enhanced maturational factors (Baxter-Jones, 1995). The underlying mechanisms contributing to RAEs are likely multi-factorial in nature and include a variety of individual, task, and environmental contributors (Wattie et al., 2015). The potentially advanced physical (Gaston & Bennet, 2014; Gil et al., 2013), cognitive (Jimenez & Pain, 2008; Bisanz, Morrison, & Dunn, 1995) and social (Dhuey & Lipscomb, 2008; Thompson et al., 2004) development of these older players can lead to increased propensity for this relatively older population to be chosen for representative squads and teams. Using these factors as markers for potential future performance can result in a biased view of potential and can facilitate recruitment into advanced teams or structures for relatively older athletes. A focus on short term success over longer term development can lead to a selection bias towards those players born earlier in the year, thus creating unfair advantages within a development system, as these advantages are perpetuated throughout the key developmental stages of a youth athlete (i.e. through access to better coaching facilities, higher competition and exposure to scouts).

So let’s dive into the RAE in female football – is it as common a feature as it is in the male youth game?

U17 UEFA tournaments 2019

In 2019, I conducted an analysis of the dates of births of the male footballers that were listed on the official programme for the 16 teams that qualified for the UEFA U17 championship. A significant RAE was evident within that sample (read more here https://talentdevelopmentinirishfootball.com/2019/05/09/relative-age-effect-in-uefa-u17-championships-2019/ ). I conducted a similar analysis of the female U17 UEFA 2019 tournament. The final stages consisted of 8 teams (Bulgaria (hosts), England, Netherlands, Spain, Germany, Portugal, Denmark and Austria). 117 players were born in 2002, with 35 born in 2003 and 8 born in 2004. A comparison of male and female U17 RAE figures are below, broken down into quarters (I.e. Jan/Feb/March is Q1).

So RAE in both tournaments differed, why?

In their analysis of all female RAE studies from 1984-2016, Smith et al. (2018) found a small but significant RAE when all 57 studies were pooled. When compared to similar studies on male sport, the RAE magnitude was smaller for female sport (Cobley et al., 2009).  The magnitude of RAE was higher in pre-adolescent (≤ 11 years) and adolescent (12-14 years) age groups and at higher competition levels. RAE magnitudes were higher in team based and individual sport contexts associated with high physiological demands. An interesting observation in this study was that the highest risk of RAE was associated with the youngest age category (≤ 11 years). This emergence of RAE pre-maturation is earlier than the usual peak of difference in males which tends to come during / post rapid growth phases in adolescence.

In male youth football, studies consistently show a RAE with an over-representation of players born at the beginning of their cohort year. The literature shows inconsistent results when comparing male and female samples in football. For example, Vincent and Glamser (2006) showed gender differences of the RAE of 17-year-old football players; with an RAE in males, but not in females. Conversely Götze and Hoppe (2021) found that that RAEs exist in German elite adult female and male soccer but was more prominent among males. Helsen et al. (2005) showed consistent RAEs for male and female soccer players in the U18 European championships.

There are also conflicting results regarding RAEs in female football. For example, there was no statistically significant RAE in elite female soccer in the US Soccer Federation (Vincent & Glamser, 2006), French professional championship (Delorme et al., 2009), or the Swiss national teams (Romann & Fuchslocher, 2011). However, other studies have found a significant RAE (Baker et al., 2009; Sedano et al., 2015). Romann and Fuchslocher (2013) found variations within a tournament in terms of the squad lists for teams at two FIFA U17 Women’s World Cups, with Ireland, Ghana, Nigeria and Trinidad and Tobago the only teams showing a significant RAE. Korgaokar et al. (2018) found a RAE across all age groups (U14-U18) of female players competing in the ‘Elite Clubs National League’ in the US. Like most male studies of RAE, this effect lessened as players get older. Along with finding a RAE in U18 Chinese female football, albeit not as large as the male cohort, Li et al., (2020) noted the strongest effect was present among goal-keepers.

Although tentative in nature, Smith (2019) found a link between ‘commitment to learning’ and relative age in post-adolescent female football sample. Relatively younger players displayed higher markers in both motivation to learn and active engagement in the learning process. This provides a base for future research to explore reasons behind a ‘reversal’ of the RAE which has been noted in some contexts resulting from developmental challenges or experiences (cf. McCarthy et al., 2016).

Why is there a difference?

When faced with limited female data, the above graph can be a useful guide to evaluate the current evidence base against, focusing on the female athlete and the female sporting environment. Therefore to attempt to understand why RAE is not as consistent in female football it should be explored from a number of viewpoints as RAE is the result of “a mixture of physical, cognitive, emotional, and motivational causes work together to produce the effect” (Musch & Grondin, 2001, p. 159). Possible explanations for gender-specific differences of the RAE can be related to variations of competition levels and the interaction of maturational and biological differences with socialization effects (Vincent and Glamser, 2006; Baker et al., 2010; Nakata and Sakamoto, 2012).

Parents and self-deselection?

Female players born in the first half of the selection year may be more likely to begin playing soccer earlier compared to their younger counterparts (Romann, 2013). Some evidence suggests parents may be hesitant to register a later-born child in the early years of participation, as reflected in lower registration numbers of relatively younger participants (Smith & Weir, 2013). Additionally, they are more likely to drop out and become unavailable for selection (Delorme et al., 2010). Therefore, more research is needed to investigate the impact of RAEs among all registered female players along the development pathway to identify patterns related to initial enrollment and dropout (cf Smith, 2019).

Depth of competition?

The ‘depth of competition’ hypothesis describes how the ratio of players available for squads and positions could influence an individual’s likelihood of participating in or being selected for the squad. If a high number of players are competing for a small number of playing opportunities then the level of competition experienced by players trying to obtain a position is inflated, potentially magnifying the influence of RAE within a cohort. Less intense competition to make a team can have an impact on RAE figures (Götze & Hoppe, 2021; Finnegan et al., 2016). In a less popular sport, the number of available athletes is reduced and the demand for positions is not as great (Schorer et al., 2009). Therefore, it is expected to have a smaller RAE when fewer athletes participate in the sport as the demand for positions is not as great.

Korgaoker et al., (2018) postulate that their strong and consistent RAE found in U14 – U18 ECNL in the US was due to the popularity of the sport and competition for places in this context in comparison to female football in other places (i.e. of the 4.8 million registered female soccer players worldwide in 2014, approximately half came from the USA and Canada) (FIFA Women’s Football Survey, 2014).. Supporting the idea that competition increases RAE, Lagestad et al., (2018) found that the level of RAE became greater as females progressed through the stages from local clubs to a regional team in Norwegian football.

The presence of RAE at various levels cast some doubt on this theory being the sole reason behind a RAE as it has also been identified in situations where athlete selection on the basis of perceived talent would not yet play a role like in non-competitive grade, 7 year old groups (cf. Delorme & Raspaud, 2009).

Biological and sociological interactions

As I mentioned above, RAE and biological maturation are two separate constructs but it is still worth exploring the potential impact that maturation has on female sport as Baxter-Jones (1995) suggested that the sex difference in RAE is the result of an earlier maturation of girls and a higher variance in the degree of maturity among boys. The average age for puberty for girls is 11 (but can begin any time between 8 – 14 years old), with changes being broader than just physical (see graph below). For example, the average weight gain for adolescent females ranges from 5.5–10.5 kg per year, they experience an average growth in height of 8 cm per year, with a range of 6–10.5 cm per year, continue to gain fat mass with proportionately more fat concentrated on the lower body (Needleman, 2000;  Pápai, 2012). Early maturing adolescent females tend to initially be taller and have greater fat mass. These physical features may give a modest (if any) advantage in sports and actually may lead to difficulty with particular motor tasks (Brown et al., 2017). In his study of regional level football league in the US, Kirkendall (2014) found that female RAE was most significant around puberty ages.

Since girls mature earlier than boys, the prevalence pattern of RAEs would be different between female and male athletes (Nakata & Sakamoto, 2012). If a development programme was beginning at age 14/15, then perhaps the potential impact of maturity would be lessened as there would be a greater chance that more of the female cohort had already gone through their growth spurt, with the benefits essentially having leveled out more than boys at that age (Baxter-Jones, 1995).  

In his former role as US Soccer High Performance Director, James Bunce noted in this seminar (https://www.ussoccer.com/bendthecurve/webinars ) a difference between boys and girls selected to regional squads. In the female cohort at U 14, there was only one early maturing girl and girls were very close to their adult height. The boys group was stacked with early maturers (marked in yellow in the below table images) and were still some way off their full adult height. The High Performance team suggested that as females go through puberty, a hormonal response is to put on mass, this impacts athletic ability quite significantly, and that perhaps those early maturers are not being selected (or are de-selected) due to a perceived lack of athleticism. For athletes where that was offset for longer, those late maturing athletes remained in the club, receiving more training and were retained even when they eventually went go through their spurt due to having been in the club for longer. The importance of treating this topic sensitively with females is also noted. There may also be some work to do here in wider research surrounding the validation of female specific databases for estimating maturity.

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The ‘maturation-selection’ hypothesis is most commonly cited by researchers to explain RAE (Baker et al., 2010; Lovell et al., 2015). This hypothesis suggests that advanced chronological age is accompanied by greater anthropometric (e.g., stature) and physical attributes (e.g., muscular strength and endurance) which provide performance advantages in many sport contexts. These differences are further exacerbated during adolescence. Consequently, relatively older children who are likely to be further along in terms of maturational development, receive more attention from coaches and may experience a higher likelihood of selection for elite levels of sport competition, which ultimately furthers their athletic development. Conversely, relatively younger participants may not have the same opportunity to develop and are more likely to struggle with perceptions of competence and self-worth (Delorme et al., 2010; Helsen et al., 1998). It is worth noting that RAE and biological maturation are two separate concepts and being relatively older is no guarantee of these enhanced physical characteristics!

Conversely, if early physical development acts as an important advantage for young males in many sports, it may also act as a socially constructed disadvantage for young females that could facilitate their dropout from sports activities (Delorme et al., 2009). Perhaps the adaptation to puberty related physical changes may lead to drop-out for girls due to feelings of being watched or judged and shyness regarding body changes (e.g. breast development, hair growth, onset of period, increasing fat mass). Vincent and Glamser (2006) argued that social pressures to conform to a socially constructed gender role (i.e., stereotyped definition of femininity) could make early maturing females less motivated to achieve excellence in a competitive sport because they perceive that society does not value female athletic accomplishments as much as male ones.

So what?

• This short dive into female RAEs highlights the need to look at established sport science ‘knowledge’ and assess how relevant it is for the female population.

• If the ‘relatively youngest’ cohort in teenage female footballers are more likely to dropout from football (Smith, 2019), then this should be noted as a potential issue for coaches of this age-group to monitor and utilise appropriate intervention strategies.

• Coaches should be aware of the differing maturation journeys for both girls and boys, both from a physiological and psychological perspective. Coach education around this topic should contain information on the development of both males and females.

• As pressure to conform to gender-based stereotypes can lead to drop out in sport, coaches working with females of this age-group should provide role-models for female athleticism.

• The main theory of RAE is linked to competition for places, as the popularity of women’s football grows, then so might the extent of RAE within the game. Longitudinal analysis of player registration databases should be periodically analysed to assess whether RAE is increasing in magnitude in your context.

Conclusion

Concepts like RAE and maturation interact differently for girls in a sporting context than they do for boys. The prevalence of RAE in females follows a different pattern than in male football, therefore we shouldn’t superimpose potential methods to address the issue which we advocate for the male game. Greater commitment to research on women’s football will allow practitioners to develop their skillset to better fit the psychological, physical and emotional needs of female athletes.

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