ArticlePloS one2026
Cross-national and historical variation in relative age effects in professional football.
Article in PloS one, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
0 citing papers in PubMed.
No citing paper in PubMed yet.
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
1 author.
Funding
No grant is acknowledged in the PubMed record.
Abstract
The relative age effect (RAE) - the overrepresentation of players born early in the selection year - is one of the most robust findings in sports science, yet how much it varies across countries and over time remains surprisingly underexplored. Drawing on birth-date data for 49,578 male professional footballers across 44 national systems and five birth cohorts (1985-2009), this study describes three patterns that have not previously been examined together. RAE magnitude varies enormously across national football systems, ranging from close to zero to birth-quarter gaps exceeding 40 percentage points. It has also increased across successive birth cohorts: players born in 2005-2009 show birth-quarter imbalances roughly 9 percentage points wider than those born in 1985-1989. Common macro-level indicators - national footballing strength, gross domestic product (GDP) per capita, and population - show at most weak and inconsistent associations with cross-national differences in RAE and do not account for the historical increase once country and cohort are held fixed. Together, these findings provide a comparative benchmark for understanding cross-national and historical variation in relative age effects.
Indexed as
Identifiers
What OpenQuestion holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.