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Doomed to Fail in Hockey if born in Summer?

A widely debated topic in the sports world is whether or not being born in the first months of the year determine which hockey players make it to the NHL. I found the base article debating the issue on Smithsonian.org and then followed it to the actual paper. The theory that the best hockey players are born in the winter was made famous by Malcom Gladwell. Basically, players that are born after January 1, which is the age group cut-off date in Canada, a big hockey country, will be more strong and skill-established than their younger counterparts in their age group at the ages where a couple of months can make a difference in size. These older players will, which sounds plausible, be the fastest, make better teams, stand out and get better coaching, all leading towards increased skill compared to the younger players in the groups. Therefore, Malcom Gladwell claims that the NHL has more players born in the first quarter than any other year.

However, this may not be true; the matter was studied by Robert O. Deaner in depth. In hockey, players drafted to the NHL are not guaranteed a spot on the teams; more than half will never play in the league’s games. Although many coaches draft the older players, as seen below, many of them don’t live up to their expectations, because of the selection bias placed on them.  It was actually shown in a study of all of the drafted players from 1980-2006 that the players born later in the year were twice as likely to succeed in the league, even though they were often picked many slots later than the older draftees.


According to the paper by Deaner, draft selection measures the perceived talent and their performance in the league determines their realized talent. It seems to me that the older players are less likely to make it because they were chosen due to the bias that is placed on the NFL prospects. The younger players made it because they showed exceptional talent and are placed less on a pedestal because of their age and their perceived belief to be less likely to succeed, which seems to be wrong.


You can see in these graphs from the study, the productivity vs. the perceived ability.

Personal anecdote here: I met Marty St. Louis and Derek Stepan from the New York Rangers in June of this year. They are both two of the best players on the Rangers and played major roles in bringing NYR to the Stanley Cup Finals this past season. Funny enough, it was both of their birthdays, so my story further supports Deaner and his paper.