In partnership with England Rugby, this project aims to deepen our understanding of relative age effects (RAEs) in both male and female rugby union, from age-grade levels through to international representation. RAEs describe the overrepresentation of athletes born earlier in the selection year, often resulting in developmental advantages and are particularly evident in youth rugby.
The first study explored the presence of RAEs in English age-grade rugby union, analysing data from 228,206 male and 23,563 female participants aged U7 to U18. When comparing observed values with national norms, significant differences were found across all male age categories and in nine out of twelve female categories. Among males, RAEs became more pronounced from U14 onwards, potentially linked to puberty and the introduction of 15-a-side rugby. In females, a within-2-year effect emerged in the U13 and U15 categories, while an inverse within-3-year effect was observed in the U18 group, showing a higher proportion of younger players. These findings highlight the entrenched nature of RAEs in English age-grade rugby and underscore the need for gender-specific considerations in youth sport development.
The second study investigated RAEs in the male English professional and international rugby union pathways, comparing youth cohorts (U15 Regional Academy: n = 1,114; U16 to U23 England Academy: n = 849) with their respective senior cohorts (Senior Professional: n = 281; Senior International: n = 48). Analysis revealed a significant overrepresentation of relatively older players in both youth groups, with stark differences between birth quarters. However, these differences were not present in the senior cohorts. Interestingly, players born in the youngest birth quarter were 3.9 times more likely to progress to senior levels than their older peers, supporting the ‘underdog hypothesis’—the idea that relatively younger athletes may develop greater resilience and skills through early challenges. The study also highlights potential relative age solutions, such as age and anthropometric banding or flexible competition structures, to ensure a more equitable developmental environment for all players.
The third study comprised two main aims: (a) examine the birth quarter distributions of the England Rugby U18 players under two different cut-off date systems—September to August and January to December, and (b) explore the birth quarter distributions across the England Rugby international development pathway, including U18, U20, and senior teams, as well as youth players who progressed to senior representation. Analysis showed that the distribution of birthdates shifted in alignment with the specific cut-off dates, consistently favouring relatively older players. While RAEs were evident at youth levels, they were not present at the senior level. Nonetheless, more relatively older players were successfully capped during the transition from youth to senior international rugby, highlighting the long-term influence of early age-based selection advantages.
The fourth study examined RAEs in the English women’s and girls’ rugby union talent pathways, comparing youth players with their respective senior cohorts (total n = 1,367): (a) U18 England Rugby Centre of Excellence players (n = 325) vs. Senior Premiership players (n = 868), and (b) U18 England players (n = 49) vs. Senior England players (n = 125). Analysis revealed no statistically significant differences in birth quarter distributions at either youth or senior levels, nor among those who successfully transitioned between them. However, descriptive data showed skewed birthdate patterns within the youth cohorts, witch 30% of Centre of Excellence players were born in the first birth quarter compared to 20% in fourth birth quarter, and 33% vs. 18% among U18 England players. These findings suggest potential early-stage RAEs and emphasise the importance of considering gender-specific factors—such as developmental differences, participation rates, and sociocultural influences. The study also cautions against directly applying male development models to the female game, to prevent similar relative age patterns as the women’s sport continues to grow.
Based on these findings, important next steps for this project are to explore the underlying mechanisms driving RAEs across different stages of development, with particular attention to puberty, competition formats, and gender-specific factors. In practice, it will also be important to consider designing, implementing, and evaluating targeted interventions—such as age and maturity banding, flexible grouping policies, and relative age awareness training for coaches and practitioners—to create more equitable talent development environments and reduce long-term selection biases.