Is There (Still) a Relative Age Effect in Tennis?
by Ryan M. Rodenberg
As a junior tennis player in the Pacific Northwest during the late 1980’s and early 1990’s, I frequently heard players and parents talk about those stuck with “bad birthdays” and those fortunate enough to have “good birthdays.” Such talk centered on what sport scientists and academic researchers call the “relative age effect.” The relative age effect is concerned with the correlation between early year birth and athletic success given arbitrary cut-off dates for youth sport eligibility. For example, the relative age effect would be evidenced by a significantly larger number of elite players being born between January and June rather than between July and December in a sport with a January 1 eligibility cut-off date. The relative age effect is explained by athletes born in January being as much as eleven months older, and therefore more physically developed than their competitors and teammates born later in the year. Relative to their younger peers, those with January birthdays, for example, may be labeled as being better and/or or more talented. Subsequently, such youngsters would be funneled into a higher level training system featuring better coaching, competition, and opportunities for improvement and long-term success. The initial fork in the road is exacerbated through the years and becomes a self-fulfilling prophecy. In other words, there may be confusion between physical maturity and precocity, on one hand, and talent and potential, on the other hand.
In a comprehensive review of the relative age effect, Musch and Grondin (2001) summarized two instances of such effect manifesting itself in junior tennis. A similar finding was made among male and female adult tennis professionals, with 58.9% being born in the first six months of the year (Edgar & O’Donoghue, 2005). The authors concluded that the cut-off date “is responsible for the skewed birth date distribution in tennis rather than regional or climatic factors” (p. 1013). Since my junior tennis days, the USTA has moved away from a static cut-off date and opted for a rolling age deadline in junior tennis. Has such move dissipated any residual relative age effect? Does the relative age effect still subsist internationally in the ITF junior rankings? Irrespective of the answer to either of the foregoing (unanswered) questions, it is interesting to query whether any lingering relative age effect is meaningful in college tennis and beyond. Based on research outside of sports, the answer appears to be that it is.
Specifically, the relative age effect has been investigated as an economic function focused on an individual’s “age of entry.” Bauer and Riphahn (2009) found that early schooling has a positive effect in the form of increased educational mobility later in life. Similarly, Bedard and Dhuey (2006) concluded that relatively early age at school entry had a positive effect on pupils’ long-term educational performance. Pointedly, due to the adoption of a single cut-off date, the authors observed that at the age of school entry (e.g. kindergarten), the oldest children were roughly 20% older than the youngest children. Bedard and Dhuey found that such initial maturity differences have long-lasting educational effects that did not dissipate. Namely, the youngest members of the cohort scored lower on standardized tests in both fourth grade and eighth grade and were less likely to attend college upon graduation from high school. In addition to the positive educational effects, early age of entry relative to school cut-off dates has also been found to boost leadership qualities (Dhuey and Lipscomb, 2008). Further, states that have changed their cut-off dates to earlier in the school year have seen an increase in adult earnings (Bedard and Dhuey, 2007). These non-sport studies indicate that the long-run effects of relative age differences early in life may persist for decades or more – athletically and otherwise.
Bauer, P.C. & Riphahn, R.T. (2009). Age at school entry and intergenerational educational
mobility. Unpublished manuscript.
Bedard, K. & Dhuey, E. (2007). Is September better than January? The effect of minimum
school entry age laws on adult earnings. Unpublished manuscript.
Bedard, K. & Dhuey, E. (2006). The persistence of early childhood maturity: International
evidence of long-run age effects. The Quarterly Journal of Economics, 121(4), 1437-
Dhuey, E. & Lipscomb, S. (2008). What makes a leader? Relative age and high school
leadership. Economics of Education Review, 27(2), 173-183.
Edgar, S. & O’Donoghue, P. (2005). Season of birth distribution of elite tennis players. Journal
of Sports Sciences, 23(10), 1013-1020.
Musch, J. & Grondin, S. (2001). Unequal competition as an impediment to personal
development: A review of the relative age effect in sport. Developmental Review, 21,
Ryan M. Rodenberg teaches sports law at Indiana University-Bloomington and is the volunteer assistant women’s tennis coach for the Hoosiers. He can be reached at email@example.com.