Jenson Button, Lewis Hamilton and Michael Schumacher. Toni Kroos, Victor Valdes and David Silva. All are world champions in their respective sports. All were born in January. While this might seem like a coincidence, a growing body of work into this area known as relative age effects now suggest when you are born actually matters!
Assuming a January 1st cut-off date, a person born in the earlier will generally have a physical advantage over somebody born later in the year. Take January and November for example. This ten month difference in birth dates at Under-12 level represents about 8% of the players total life time – a significant amount of time. Footballers generally, though anecdotally, reach their peak between the year 25 and 29. At this stage a 10 month difference counts for about 3% of total life time. Once players begin a professional career the difference in physicality and performance may be long eroded but the key point is the beginning of the career.
Data has been analysed across 30 different elite leagues around the globe and unsurprisingly the numbers favour players born in the first half of the year. There is one notable exception to this however – England. This is because the cut off for birthdays in junior level is taken in September rather than January. The average birth date of elite players in their respective leagues are all in the first six months of the year. In England it’s in the second half of the year.
Across Europe the average birthdate of a citizen is the 1st of July – more or less in the middle of the year. The average birthdate for a professional footballer across 31 of Europe's top leagues is the 9th of May. The data table demonstrates a relatively even spread of birthdates for Europe’s citizens. There are more than 10 percentage point’s difference between the numbers of professional footballers born in the first quarter of the year versus the last quarter with the trend throughout the year being downward.