But there's good news. The PLOS ONE study showed that coaches who favor older players put their teams at a disadvantage. It found that despite making up only 34% of draftees, players born between July and December scored 44% of the points. These relatively younger players also went on to have longer careers than their older counterparts. This shows that just having knowledge of the relative age effect can bias coaches, and the smart way to go is to judge a player purely on performance. Learn more about this in the videos below.
Age differences might not matter that much to adults, but among kids, they're significant—even when it comes to the difference between being born in January and December of the same year. For team sports such as hockey and soccer, the age cutoff for a kids' team is often the calendar year. This means that children born in January will be on the same team as children born in December, giving them an age difference of nearly a year. That year can be a huge leg up when it comes to both physical and mental development, especially at a young age, and studies find that this advantage follows children throughout their athletic careers. A 2013 study in the journal PLOS ONE cited the fact that in the National Hockey League (NHL), 40% of professional players are born in the first quarter of the year. This climbs to 50% on elite youth soccer teams, according to Stephen J. Dubner and Steven D. Levitt of Freakonomics. The effect even holds up in the classroom, where children born in summer months—right before the fall birthday cutoff—are generally seen as academic underachievers.
The Seasonal Birth Effect
The time of year you're born has other effects, too.
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Key Facts In This Video
If you were born in the summer, research suggests you're more likely to be a smoker or shortsighted. 00:34
Increased exposure to sunlight in women who get pregnant in the summer may raise the likelihood of left-handedness and schizophrenia in their children. 01:22
The seasonal birth effect is only visible when looking at large populations, and no causal links between birth dates and characteristics have yet been found. 02:43
How Your Birth Date Affects Your Personality
Hungarian researchers have found a link between birth month and various mood disorders.
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Does Birth Order Affect Your Personality?
Find out if being the oldest or the youngest child means something about who you are.