Dropped Out Before They Ever Competed: A Population-Wide Registry Analysis of Relative Age Effects in Norwegian Track and Field from Age 10 to 25.

Authors

Atle G Guttormsen

Published in

Sports medicine - open. Volume 12. Issue 1. Nov 06, 2026. Epub Nov 06, 2026.

Abstract

Relative age effects (RAEs), the overrepresentation of children born early in the selection year among participants in age-graded sport, shape who enters organised youth sport and who remains in it. The dominant theoretical account locates the generation of RAEs in adolescent talent-selection cycles, predicting amplification through adolescence. If selection instead occurs before children enter organised sport, participation-level inequities would need to be addressed at the entry stage rather than at adolescent talent identification. I tested this prediction using population-wide registry data 2011-2026 from the Norwegian Athletics Federation (87 624 athletes; 1 395 788 performances; the entire competing cohort), comparing birth-quarter distributions across ages 10-25 against monthly birth counts from Statistics Norway. Logistic regression with sex $\times$ age interaction tested for adolescent amplification; Manski-style bounds quantified the influence of athletes appearing briefly without a recorded birth date (61% at ages 10-12; overwhelmingly short-career early leavers).
At age 10, the youngest registered competition age, Q1 comprised 28.3% and Q4 19.7% of competitors, against population baselines of 24.6% and 22.9% ( ${\chi }^2=79.9$ , $p<{10}^{-15}$ , Cohen's $w=0.10$ ). The Q1/Q4 ratio of 1.44 showed no upward age trend through 25 (range 1.36-1.75), and restricting the analysis to ages 13-25, where birth-date coverage is 89-99%, gave the same conclusion. Logistic regression did not support the cumulative-advantage prediction in females ( ${\beta }_{\mathrm{age}}=-0.007$ , $p=0.46$ ), showing only a mild curvilinear elevation in males peaking at age 18-19 ( $p=1.0\times {10}^{-5}$ for the sex $\times$ age interaction). First-year retention from age 10 was nearly identical across quarters (Q1-Q4 gap 2-3 pp), confirming the skew was not produced by differential dropout within the registry. Findings were robust to exclusion of the COVID-19 pandemic years.
In a population-wide individual sport without team selection, the birth-quarter skew is established by age 10 and stable through senior level. This pattern is inconsistent with the cumulative-advantage prediction and points to pre-entry selection. I hypothesise that mastery experience through measurable personal progress retains surviving athletes, a feature less available in team-sport contexts. These findings support directing, and evaluating, efforts to reduce relative-age-related participation inequities at the sport-entry transition rather than only at adolescent talent-identification stages; testing this account in other individual sports and countries is a priority.

PMID:
42993455
Bibliographic data and abstract were imported from PubMed on 07 Nov 2026.

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