Have you read "Outliers" from Malcolm Gladwell? There he was mentioning that most of the successful hockey players have a pattern in their birthdays and I found

Have you read "Outliers" from Malcolm Gladwell? There he was mentioning that most of the successful hockey players have a pattern in their birthdays and I found it quite similar: "in any elite group of hockey players the very best of the best 40 percent of the players will have been born between January and March,30 percent between April and June, 20 percent between July and September, and 10 percent between October and December." "The explanation for this is quite simple. It has nothing to do with astrology, nor is there anything magical about the first three months of the year. It's simply that in Canada the eligibility cut off for age class hockey is January 1. A boy who turns ten on January2, then, could be playing along side someone who doesn't turn ten until the end of the year and at that age, in preadolescence, a twelve­ month gap in age represents anenormous difference in physical maturity."