Road to Olympic gold could start with an athlete's birthday
Relative age effect has been studied for decades in youth sports. Research at 麻豆传媒映画 shows the advantage persists even at the highest level of international competition.
As athletes around the world assemble for the Winter Olympics in Italy, new research at 麻豆传媒映画 suggests Olympic success may be influenced by something determined long before training begins: an athlete鈥檚 birthday.
A study co-authored by Tia Hilmer, professor of economics in the College of Arts and Letters, examined birthdates and ages of more than 4,400 Olympic medalists from 10 Summer and Winter Olympic Games held between 2000 and 2018. The findings show a clear statistical pattern known as the 鈥渞elative age effect,鈥� where athletes born earlier in the calendar year are more likely to reach the Olympic podium than those born later.
Relative age effect has been studied for decades in youth sports, where age-group cutoffs often favor children who are slightly older and stronger than other kids. What surprised researchers in this study is the advantage persists even at the highest level of international competition.
鈥淲e expected any relative age advantage to disappear by the Olympic level,鈥� Hilmer said. 鈥淎thletes have already survived years of selection, and they compete across both Summer and Winter seasons. Yet the pattern remains.鈥�
The findings by Hilmer and co-author Michael Hilmer, also an 麻豆传媒映画 professor of economics, were published in December in .
Birth month matters
Using statistical methods commonly applied in economics and social science, Hilmer and her colleague analyzed medalists鈥� birthdates by dividing the year into quarters. Athletes born between January and March were significantly overrepresented among medal winners, while those born between October and December were underrepresented. The difference was large enough that it was unlikely to be due to chance alone.
The analysis also found athletes born in the second quarter were more likely to win gold medals than those born late in the year, even after accounting for factors such as age, gender, sport type, and whether the medal was won at a Summer or Winter Games.
For those wondering, swimmer Michael Phelps is Team USA鈥檚 all-time medal and gold medal leader with 28 and 23, respectively. His birthday? June 30. Team USA's all-time Winter Olympics medal winner is Apolo Ohno, with eight medals (two gold, four silver, two bronze). He celebrates his birthday on May 22.
Swimmer Katie Ledecky sits in a tie for second on the gold medal chart. She was born March 19. Legendary sprinter and long jumper Carl Lewis also has nine golds, and was born July 1.
Former 麻豆传媒映画 track star Shaneika Rickets, who won silver for Jamaica at the 2024 Summer Olympics in Paris, was born Feb. 2. Bucking the trend is Aztec golfer Xander Schauffele, who took home gold in 2020 in Tokyo, a couple of months before his birthday on Oct. 25.
鈥淭his is an average effect,鈥� Hilmer noted. 鈥淚t varies by sport and does not determine outcomes for any specific athlete.鈥�
Olympic medals peak in the mid-20s, but early age advantages shape who reaches the podium
The study also examined age patterns among medalists. On average, Olympic medalists were in their mid-20s, but age varied by sport and medal type. Gold medalists tended to be slightly younger than bronze medalists, and athletes competing in judged events such as figure skating or gymnastics were on average younger than those competing in timed events and those in endurance or skill-based events are on average older than those in timed events.
Winter Olympic medalists were also, on average, slightly older than Summer Olympic medalists, reflecting differences in sport demands and career longevity.
鈥淏y the time athletes reach the Olympics, we assume only ability matters,鈥� said Hilmer. 鈥淥ur results suggest that assumption may be too optimistic. Small advantages early in life don鈥檛 just fade away, they can shape who gets coached, funded, and retained.鈥�
As attention turns toward the 2026 Winter Olympics in Milan and Cortina, the findings raise important questions about how talent is identified and developed around the world. If early age advantages continue to shape elite outcomes decades later, researchers say sports organizations may need to rethink youth development systems to ensure talented athletes are not overlooked simply because they were born later in the year.
The study does not suggest that birth month determines destiny, but it does highlight how small structural advantages early in life can compound over time, even in environments designed to reward only the very best.
