Season-of-birth eﬀects on elite junior tennis players’ world rankings
Skewed month-of-birth distributions have been discovered in many sports including Ice hockey (Barnsley et al., 1985; Boucher and Mutimer, 1994), soccer (Brewer et al., 1995) and basketball (Thompson et al., 1991). A skewed month-of-birth distribution will typically have more players who were born in one quarter of the year than any other and there will be a decreasing number of players who were born in the successive quarters. There is a skewed monthof-birth distribution of tennis players participating in the singles events of Grand Slam tournaments with more players than expected being born in the ﬁrst half of the calendar year (Edgar and O’Donoghue, 2005). It is thought that the International Tennis Federation (ITF) cut-oﬀ date of 1 January is responsible for this skewed month-of-birth distribution. Indeed, there is considerable evidence that the skewed month-of-birth distributions observed in soccer participants result from the cut-oﬀ date for the junior competition year (Brewer et al., 1995; Musch and Hay, 1999). Simmons and Paul (2001) noted that the England schoolboy soccer international squad and players from the English Football Association youth squad had diﬀerent skewed month-of-birth distributions that were associated with the two diﬀerent cutoﬀ dates that applied. Musch and Hay (1999) found that month-of-birth distributions for top league soccer players reﬂected the cut-oﬀ date for junior competition in Australia, Brazil, Germany and Japan unaﬀected by the different hemispheres, climates and cultures of those countries. Furthermore, when the start date of the junior competition year in Australia changed, it eventually produced a corresponding shift in the distribution of month-ofbirth of participants. Previous research into season-of-birth eﬀects on tennis participation has been based on cross-sectional studies (Dudink, 1994; Baxter-Jones, 1995; Edgar and O’Donoghue, 2005) rather than tracing the participation of players over time. Therefore, a longitudinal programme of research has commenced to track the participation of players over the course of their careers. This will allow changes in participation levels and success of players born in diﬀerent parts of the year to be compared. Speciﬁcally two groups will be compared; those born in H1 (from 1 January to 30 June
The purpose of the current paper is to report on the ﬁrst three years of the longitudinal study.