Birth Quarter, Playing Position, and Market Value in Elite International Football: Evidence from the FIFA World Cup 2026

The relative age effect is well documented in football, but unequal birth-quarter representation does not necessarily translate into positional or economic differences among elite players. This study examined associations between birth quarter, playing position, and market value among 1248 players from the 48 national teams participating in the 2026 FIFA World Cup. Publicly available FIFA and Transfermarkt data, with market valuations retrieved on 10 August 2026, were analysed using chi-square goodness-of-fit tests, multivariable logistic regression, and linear models adjusted for age, height, continental confederation, and, for market value, age2 and playing position. Economic analyses included 827 players and incorporated a national-team random intercept. Players born early in the year were overrepresented, but no birth-quarter comparisons in the primary adjusted models reached statistical significance for playing position or market value. For goalkeepers, the comparison between the fourth (Q4) and first (Q1) birth quarters yielded an odds ratio of 0.53 (95% confidence interval: 0.28–1.01). Adjusted market-value differences relative to Q1 were +15.9% for the second birth quarter (Q2), −1.4% for the third (Q3), and +10.7% for Q4. National-team clustering accounted for 35.2% of the residual variance in log-transformed market value not explained by the fixed effects. These findings distinguish unequal representation from adjusted positional and economic associations within an already selected elite sample. However, confidence intervals included potentially relevant associations, and the cross-sectional design cannot establish how relative age influences earlier selection and progression.