Relative age effect amongst footballers in the English Premier League and English Football League, 2010-2011

Many studies have shown that a relative age effect exists in different sports – that is to say, birth dates of participants in particular sports are skewed towards the start of the competitive season. This study examines the relative age effect for the 2828 professional footballers in the English Premier League, the Championship, League One and League Two during the 2009-2010 season. Using dates of birth for all players from the Sky Sports Football Yearbook 2010-2011, the Chi squared goodness of fit test was used to determine relative age effect within the four leagues. A comparison was also made with birth dates for the general population from the Census and population projection data. The relative age effect was then examined for each of the leagues, and then for differences between the leagues. The results showed that: (i) there was a difference between professional footballers and the general population (p < 0.001); (ii) there was a relative age effect in the Premier League (p = 0.03), and a stronger age effect in the other three leagues (p < 0.001); and (iii) there was a difference between the Premier League and League Two (p = 0.002).