Malcolm Gladwell capitalized on research conducted by Roger Barnsley (et al., 1985) by suggesting in his 2008 book, Outliers, that there is an “Iron Law of Canadian Hockey.” This theory is also known as the relative age effect in psychological research and it suggests that the older a player is when they begin training for a sport, the more likely they are to achieve success in that sport.
In fact, in a talk posted on YouTube, Gladwell goes even further, saying, “In absolutely every system in which hockey is played, a hugely disproportionate number of hockey players are born in the first half of the year.” He says this in the context of a talk about society not taking advantage of opportunities to improve human potential.
“Logic tells us there should be as many great hockey players born in the second half of the year,” suggests Gladwell, “as born in the first half. But what we can see here, there’s almost no one born it the end of the year, everyone’s from the beginning.”
But is this actually true — are more elite hockey players born in the first half versus the second half of the year?