Relative Age Effect in Youth Baseball

It should be no surprise that the relative age effect (RAE) is alive and well in youth baseball. The RAE is well documented across sports. It posits that older players are overrepresented on elite teams in their playing age classification relative to younger players because they’re more advanced in their physical maturation. Well researched studies on this phenomenon include a 2020 article in Frontiers in Psychology, which concludes that short-term performance is impacted by the effect, but long-term is not and a JSCR article that shows that the RAE impacts the MLB draft with a bias for older athletes. This college project has similar findings.

If we look at the highest level of youth baseball, we see the RAE play out as well. USA Baseball runs an annual talent identification process called NTIS. It screens players at the state, regional and national level as part of the National Team formation process. Qualification for this year’s 12u team is based on being born after January 1, 2009. The graph below shows the age distribution of players who made the semi-final round of the team trials and illustrates the effect. Of the 192 players who attended the August 2021 NTIS tryout, 119 or 62%, were born in the first half of the year. October, November and December births were the lowest with only 26 players represented from those months from that quarter. Unfortunately, the publicly available data is based on the third round, so it’s not possible to know the distribution of births from the state and regional level tryouts to determine if the distribution was even to begin with and then began to shift earlier in the year with each progressive cut.

The NTIS selects 12 players from the 192, who are then combined with 24 from the Futures Invitational tournament to form the 36 man Trials roster. The 36 is reduced to a final 18 man roster to form the 2021 US National Baseball Team roster. As can be seen from the graph below, the RAE is even more pronounced with 50% of the team born between January and March and only one player born in the forth quarter of 2009.

The players in the latter half of the year therefore had to outperform those who had several month of additional physical and skill development. These include Derek Vazquez (PG), Julian Martinez (PG), Jacob Seamon (Twitter, PG, Instagram), Hudson Brown (PG, Instagram) and Easton Brunson (PG) from youngest to oldest.

The US National Team Committee’s job is to put the best team on the field in preparation for international competition. As can be seen from the data shown, as with other sports, this team tends to skew toward older players, who may not develop into the best athletes in the longer term.

You can read more about the relative age effect and its impact on the draft in Rany Jazayerli‘s articles on the topic called Doctoring the Numbers Part 1 and Part 2 where he explains why younger draftees tend to outperform and create more value relative to older draft picks