Thursday, May 15, 2008

The “Age-Effect” in US Soccer

For years, researchers have been interested in a youth sports phenomenon called the “age-effect”. The age-effect holds that players selected to teams tend to be the older players for their age group. That is, most players on a team tend to be born in the months closest to the cut-off for that age group. For Olympic Development Program pools, this is the first 2-3 months of the year. For club teams this is the months of August, September and October. As players are separated into age groups, some players may differ in age by nearly a year. At the youth level, a year of physical growth and maturity can make a tremendous different in the level of play. Youth athletes born in January tend to have greater body mass, height, strength and speed than their December counterparts. Thus, they are often identified as being more talented. Several studies show an age-effect in a variety of sports as well as in academic settings. Researchers have found a relative age bias with talent identification in soccer, tennis, hockey, dance and some musical performances. This is particularly evident in young boys.

This post raises the question, “Is there an age-effect in soccer?” A quick survey of US national team pools suggests that this bias is alive and well and may have consequences for player development.

The US Soccer Federation posts player pool rosters on their website. A quick survey of the boys U15 and older pools clearly shows an age-effect pattern in the selection of national pools (rosters downloaded May 2008). For the U15 pool, more than half of the U15 national pool players were born in January and February. By comparison, only 7% or 2 players were born in the latter months of October, November and December.

A similar pattern holds for the other age groups as well as the National Team pool. This is evident in the two graphs. The first graph shows the percentage of each pool born in each month (click the graph to enlarge). There is an undeniable trend towards selection of older players as a greater percentage are born in the early months of the year. Interestingly, at some age groups, there is a small increase in the percentage of players born in August, compared to July and September. August 1 is the oldest birth date for USYSA club teams and players born in August would be the oldest on their individual club teams. A more simplified view of the results is shown in the second graph. This graph collapses all the data for each pool and shows the percentage of players born in each quarter of the year. Here the results are more striking. On average, nearly half (42%) of the national pool players were born in the first quarter of the year.

On the women’s side, there is an age-effect trend, but the bias is much less pronounced. At the youngest age group (U15), nearly half of the players were born in March or earlier. However, for the older pools, the median birth month shifts from the first quarter of the year to closer to mid year. At the National Team level, the distribution of birth months is much more uniform, across all months.

To see if the age-effect in boys is a US phenomenon, the player birth dates were examined for the U15 teams of the Italian Serie A. Of the clubs currently in Serie A, 10 use the Internet to post player rosters with birth data (May 2008). At this age group, nearly half of the players, 49%, were born in the first quarter of the year and only 7% born in that last quarter. So, this age-effect in boys is not unique to the US but seems to occur internationally.

Is it possible that more talented players are both in the early months compared to the last part of the year? Yes, but highly unlikely. The age-effect trends probably reflect coaches’ preference to select more physically and psychologically mature players. In general, a player born in January will out perform his December-born competitor. Part of this difference may be due to talent, but an important component of performance is maturity. It is also likely that the age-effect trend get perpetuated as players grow older. Once selected, older players receive advanced training and the younger athletes return to their club. Thus, the gap between older and younger players persists and may even widen. This idea may be reflected in the selection of the Men’s National Team pool. At the adult level, the age-effect should be less important. An 11-12 month age difference is minimized as all players mature their mid-20s. Yet the age effect persists. Perhaps this is the result of the early birth month players being selected for advanced training early in their careers and having more developmental opportunities than their late birth month counterparts.

What does this mean and what should be done? It is important to point out that this post is not meant as a criticism of the US youth national teams selection process. It is meant to raise awareness that a bias towards older players seems to exit at many levels, including the National Team and more pronounced in males. It is also meant to emphasize the need to consider the relative age of a player when evaluating talent and potential for development. If the coach’s goal is to field the best possible team, then the best players should be selected, regardless of birth date or potential. This may indeed be the case with high school and college teams where development is less emphasized. However, if player development is the main objective, then coaches should take into account players’ birth month when selecting the player pool. Coaches should remember that they may be comparing players who have nearly a year of growth difference. For example, a player born in December whose skill level is equal to his January counterpart may actually develop into a more outstanding player once both reach the same level of physical and psychological maturity. There are numerous examples of young 14 year old players who are very skilled but get overlooked because they are less physically mature than the older players. In many cases, these players eventually mature into very gifted athletes. So, it is critically important for coaches to identify both talent and potential when selecting players to advanced training programs such as ODP and national team pools.

The age-effect seems to be a real phenomenon in youth soccer, particularly in males at the US national pool level. As such, coaches should be aware that players mature at very different rates and, during the selection process. They may be evaluating players who differ in age by nearly a year, an effect that can have a pronounced effect on what is considered “talent”. Thus, coaches should consider the relative age of the player as well and his/her current level of play.