Do Late-Born Kids Go Further in Sport?

Look at twenty years of Germany’s under-17 national football squads. About half the players were born in January, February or March. Fewer than one in fourteen were born in October, November or December.

That part isn’t surprising. International youth football groups players by calendar year, so a boy born on 1 January and a boy born on 31 December play in the same age group, nearly a year apart. At fourteen, a year can be a whole growth spurt. Selectors watch matches, not birth certificates, and they pick the kid who wins the ball.

The surprising part comes later.

The finding

In a 2024 study, Paolo Brustio, Alexander McAuley, Alexandru Ungureanu and Adam Kelly looked at 9,527 players in the men’s national teams of England, France, Germany, Italy and Spain, from 2002 to 2022.

At under-17, four of the five countries had roughly half their squads born in the first quarter of the year and 7–8% in the last. England was less lopsided: about 40% against 17%. By senior level the skew had weakened. It was no longer significant in France or Germany.

Then they followed 3,001 players born between 1985 and 1998 to see who reached the senior team. Of the under-17 players born January to March, 9% went on to a senior call-up. Of those born October to December, 16%.

You’ll see this reported as “twice as likely.” That’s the odds ratio (1.98). In plain chances, it’s about one in eleven against one in six. Still a big gap.

At under-19 the gap was smaller (15% against 20%) and right on the edge of what could be chance. At under-21 there was no clear difference.

Two stories, same numbers

The underdog story. This is the authors’ own explanation. Being the youngest for years forces you to learn the game rather than win it with your body: look up early, play in one touch, cope with being dropped. When everyone stops growing, those habits remain. The authors suggest the experience may build “a higher degree of psychological resilience and toughness.”

The filter story. A late-born kid can’t just be as good as an older teammate to get picked. He has to be clearly better, good enough to beat a year of growth. So the late-born kids in a squad are the very top of their group, while the early-born kids include some who are simply big. Of course a bigger share of the late-born group goes on. No toughness required.

Both stories predict exactly the same thing: fewer late-born kids picked, more of them succeeding. A squad list can’t tell them apart.

Better data doesn’t settle it either

Performance data agrees there’s a reversal. Fumarco and colleagues (2017) studied about 2,000 NHL ice hockey players over eight seasons. Among the top scorers, players born October to December scored about nine more points a season than those born January to March. Among the top earners, they were paid 51% more (US dollars, North American league). But the authors put effort and talent side by side and don’t choose. A filter that lets through only the most talented late-born kids also produces better late-born players.

Some data finds no reversal at all. Doyle and Bottomley (2018) took the world’s 1,000 most valuable footballers in 2014. Early-born players were over-represented, but birth date made no difference to what they were worth: “no evidence for a reversal.” That cuts against both stories, since both predict late-born professionals should be better. One caveat: those values come from Transfermarkt, a partly crowd-sourced database, which is also where the 2024 study’s squad lists came from.

One clue. The late-born advantage is largest at under-17 and gone by under-21, which is also where the birthday skew is weakest. If the filter is the cause, that’s what you’d expect: by 21, nobody has to beat a growth spurt to get picked. But the under-21 result is too uncertain to lean on. Treat it as a hint.

The number nobody quotes

The same 2024 paper counted senior internationals who never played for a youth national team at all. The paper’s text says 14–24% depending on country. Its own table puts Germany at 10.6%. Call it between one in ten and one in four.

Turn it around: of the under-17 internationals, at best about one in seven ever played for the senior team. In most of the five countries it was closer to one in ten.

So being picked at sixteen isn’t the start, and being left out at fifteen isn’t the end. A selection made at that age is a weak signal in both directions. That holds whichever story is right.

What the data can’t show is the kids who were dropped and stopped playing. They never reach any database, so nobody knows how many there were.

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The junior system isn’t measuring what parents think it’s measuring. It’s measuring birthday and growth spurt nearly as much as talent. The late-born kids who survive it go further. Nobody can yet say whether the struggle made them, or the filter just picked the best of them.

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Jurisdiction: the football data is men’s national teams in England, France, Germany, Italy and Spain. The hockey study is North American, and its salaries are US dollars. Nothing here is from New Zealand.

Sourcing note: “senior level” in the 2024 study means at least one senior call-up. Its squad lists, like the 2018 player values, come from Transfermarkt, a partly crowd-sourced database. No equivalent study exists for tennis, swimming or other individual sports, so don’t carry these numbers across.

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Sources: Brustio, McAuley, Ungureanu & Kelly, “Career trajectories, transition rates, and birthdate distributions: the rocky road from youth to senior level in men’s European football,” Frontiers in Sports and Active Living, 2024 · Fumarco, Gibbs, Jarvis & Rossi, “The relative age effect reversal among the National Hockey League elite,” PLOS ONE, 2017 · Doyle & Bottomley, “Relative age effect in elite soccer: More early-born players, but no better valued, and no paragon clubs or countries,” PLOS ONE, 2018.