Relative Age Effect Among Elite Youth Male Soccer Players Across the United States
Ajit Korgaokar, Richard S. Farley, Dana K. Fuller & Jennifer L. Caputo
Department of Health and Human Performance,
Middle Tennessee State University, Murfreesboro, TN
Abstract
The relative age effect (RAE) in sports is an asymmetry in birthdate
distribution where an overrepresentation of athletes born earlier in the
cohort and an underrepresentation of athletes born later in the cohort
exists. Despite a wealth of literature on RAE, few studies have examined
U.S. soccer players. Purpose: To determine the existence of a RAE
among elite youth male soccer players competing in the United State
Soccer Developmental Academy (USSDA) during the 2012-2013
season. Methods: Player birthdates (u15/u16 n = 1,724; u17/u18 n =
1,494) were collected from the USSDA website and compared to the
birthdate distribution for the general population. Player birthdates were
organized into quartiles (Q1-Q4) based upon the U.S Soccer Academy
competition year of January 1st –December 31st. Results: The data
revealed a RAE among the u15/u16 age group indicating a preference for
the selection of the oldest in the cohort. An overrepresentation of players
was observed in Q1 (34%) and an underrepresentation in Q4 (20%). The
birthdate distribution for the first (56%) and second (44%) halves of the
season showed significant differences, exhibiting a bias against the
selection of boys born between July and December in the u15/u16 age
group. No RAE was observed among the u17/u18 age group when
analyzed into quartiles or by halves of the competition year. The largest
number of players was represented in Q4 (28%) with the lowest in Q2
(19%), and the majority of the players were born in the second half of the
competition year (54%) compared to the first half
(46%). Conclusion: The current research indicated that the youngest in
elite soccer across the U.S. are disadvantaged when organized into
cohorts. Future research should focus on key factors contributing to
RAEs in youth soccer. Structural changes designed to reduce or
eliminate RAEs should be examined, evaluated, and implemented where
appropriate.
Purpose
• To determine the existence of a RAE among elite youth male
soccer players competing in the United State Soccer
Developmental Academy (USSDA) during the 2012-2013
season..
• Hypothesis: A significant RAE would be present among this
group of elite level youth soccer players, indicating a bias
against the selection of soccer players born late in the cohort
Methodology
Participants
Amateur elite youth male soccer players competing in the u15/16 (n =
1,724) and u17/18 (n = 1,494) age groups in the USSDA during the 2012-2013
season were included in this study. For the 2012/2013 season, 80 of the
highest level youth clubs across the country were selected to participate in the
Academy league. The league was comprised of 3 conferences (East, Central,
and West) and 7 divisions. Any male player within the specified birthdate
range was eligible to tryout for an Academy team regardless of place of
residence or citizenship.
Procedures
The birthdate for each player was collected from the individual team web
pages from the USSDA web site (www.academy.demosphere.com). The
birthdates of each player were compared to the birthdates of males in the
general U.S. population born during the same years as the players. The
birthdate range for the 2012/2013 USSDA player was from1994-1999. The
census birthdates were collected from the Center for Disease and Control and
Prevention (CDC) vital statistics reports, which was retrieved from the CDC
website (www.cdc.gov/nchs/vitalstats.htm). The birthdates for the players and
males in the general population were organized into quartiles based upon the
USSDA competition year of January 1st –December 31st. All birthdates were
coded as follows: Q1 = January-March, Q2 = April- June, Q3 = JulySeptember and Q4 = October-December. In addition, half-season analyses
were conducted, where the first half of the season was the combination of Q1
and Q2 and the second half of the season was Q3 and Q4
Results
The chi-square analysis indicated a statistical difference between
the observed and expected quartile distributions for all of the age
groups, indicating significant RAEs: (u15/16) χ2 (3, n = 1724) =
90.26, p < .001 and (u17/18) χ2 (3, n = 1494) = 34.17, p < .001. When
compared to the general population birth distribution, the chi-square
test and the post hoc analyses revealed an overrepresentation of
players born at the beginning of the cohort and an
underrepresentation of players born at the end of the selection year
for u15/16 age group. The standardized residuals for the u15/16 age
group showed an overrepresentation of players born in Q1 and an
underrepresentation of players born in Q2 and Q4. Among the
players in the u17/18 age group, the chi-square analyses revealed an
underrepresentation of players born toward the middle of the
selection year and an overrepresentation of players born at the
beginning and the end of the selection year. In the u17/18 age group,
the standardized residuals indicated an overrepresentation of players
born in Q1 and Q4 and an underrepresentation
Birth Quartiles for the u15/16 and u17/18 USSDA Boys’ Age Groups
Statistical Analyses
A series of chi-square (χ2) goodness-of-fit tests were used to determine
differences between the observed birth in the cohort and the expected birth
month distributions for the births of males born in the U.S. from 1994-1999
(the same years as the players). The dependent variable for each analysis was
the frequency of soccer players born in each quartile per age group. The level
of significance was set at p < .05. Statistically significant chi-square (χ2) values
were used to calculate an effect size w statistic to determine the strength of the
RAE. Post-hoc analyses were conducted for w values ≥ 0.1. Lastly, for
statistically significant chi-square (χ2) values, standardized residuals were used
to determine which observed birthdate quartiles differed from the expected
distribution (Turnnidge, Hancock, Côté, 2012). A value of ≥ 1.96 indicated an
overrepresentation of births in the quartile and a value of ≤ - 1.96 indicated an
underrepresentation of births in the quartile (Sheskin, 2003).
Conclusion
In summary, the current research indicated that the
youngest in elite soccer across the U.S. are disadvantaged when
organized into cohorts. Future research should focus on key
factors contributing to RAEs in youth soccer. Structural
changes designed to reduce or eliminate RAEs should be
examined, evaluated, and implemented where appropriate.