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If you want your kid to be a pro soccer player, pray that he or she’s born on February 5.

Today happens to be the birthday of four high-profile footballers: Carlos Tevez, Adnan Januzaj, Cristiano Ronaldo, and Neymar. Coincidence? Science thinks not. Studies have shown that the later in the year a child is born, the lower his chances are of becoming a professional.

Last year, a German career website found that of the roughly 200 players in the various German men’s national teams, from the senior side down to the U-15 squad, over a third were born in January or February—the two months with the lowest birth rates nationally. Only 12 were born in November or December. These findings line up with an earlier study that surveyed more than 25,000 young players between 12 and 18 enrolled in Germany’s youth training bases. And it’s not a uniquely German phenomenon: A study during the 2014 World Cup found that it was evident across Europe, Asia, and South America.

Scientists call it the relative age effect. Most football associations use January 1 as a cut-off date for eligibility, so a child born on January 1 will be in the same group as one born 364 days later. The older kid will probably be stronger and faster, with a deeper understanding of the game, and coaches will pay closer attention to him. As a result, he has a better chance of success from the very beginning.