Born to play? Selection Bias in Czech and Slovak Ice Hockey

Abstract

The relative age effect (RAE) is a well-established phenomenon in youth sports, where athletes born earlier in the selection year are overrepresented due to advantages in physical and psychological maturity. Previous research has consistently confirmed the presence of RAE in North American ice hockey leagues, linking it to higher selection rates and career opportunities. This study investigates the prevalence and impact of RAE in Slovak and Czech ice hockey. An 11-year retrospective analysis was conducted on 1,563 male players born between 1992 and 2002 who were selected for Slovak or Czech national teams (U16 to U20, and men’s). Descriptive statistical methods were used to compute the distribution of birth quartiles across age categories and to evaluate the progression of players to elite domestic and elite world leagues. Results confirmed a strong presence of RAE in both, Slovak and Czech junior national teams selections. However, Slovakia exhibited a reversal at the men’s national level, where relatively younger players were the most represented group. In both countries, relatively younger players showed higher rates in reaching elite domestic and elite world leagues, which suggests that early selection advantages do not guarantee professional attainment in adulthood. It highlights the need for support of late-maturing athletes and reduction of selection bias in youth selection processes.