Human inequality is not fair: NBA edition

The_Sports_Gene_Book_Cover_2013Interesting piece in The Wall Street Journal, which could have been cribbed from David Epstein’s The Sports Gene (a very good book I might add), NBA Basketball Runs in the Family (if you go to Google News and search for the title it should come up and you can get a free copy):

According to a Wall Street Journal analysis of biographical data on every NBA player, 48.8% are related to current or former elite athletes—defined as anyone who has played a sport professionally, in the NCAA or at national-team level. While other leagues feature notable dynasties—the Manning’s of the NFL or the Griffey’s in baseball—only about 17.5% of NFL players and 14.5% of MLB players are related to other elite athletes, based on a similar study.

The connectedness in the NBA likely comes down to the importance of height in elite basketball. The average NBA player is about 6-feet, 6-inches tall, which is 11 inches taller than the average American male, according to Census data.

As indicated in the piece you aren’t seeing that the 10,000 hour rule is a secret passed down within families. If you are not very tall it is unlikely that 10,000 hours of practice will result in you becoming a professional athlete in the NBA. The article emphasizes that the enrichment of those with relatives who had played in the NBA is far greater than the NFL or MLB, but please note that the average person’s odds of entering any professional sport is infinitesimal. Well, not quite, but the odds are low.

The piece in The Wall Street Journal is valuable for the added data, but there a few conceptual aspects which I’m not satisfied with. Researchers have known for decades that most of the variation in the population in non-malnourished societies in height is due to variation in genetics. 80 percent heritability is conservative. This can lead to some confused intuitions though. The correlation between siblings is high, but not that high, in the range of ~0.50. That translates to an average difference in height of nearly two inches.

41ZhyEU5lGL._SY344_BO1,204,203,200_In other words, parental or sibling success in the NBA is not destiny. On the contrary. Nearly half of current players may have had relatives who played in the NBA, but most of the people who have relatives who played in the NBA did not themselves play in the NBA. But, obviously having relatives is incredibly predictive of much higher than normal odds (orders of magnitude greater!) of becoming a professional.

Why? As noted in the article NBA players need to have an intersection of traits which are very deviated from the norm. The range restriction on height, with “very short” players being mildly above average the human male median, shrinks the pool of potential candidates a lot. Fourteen years ago James F. Crow wrote Unequal by Nature: A geneticist’s perspective on human differences. Crow observes “that whenever a society singles out individuals who are outstanding or unusual in any way, the statistical contrast between means and extremes comes to the fore.” As it happens being a professional basketball player is not just about height; one needs to also be athletic, and exhibit a modicum of agility and skill. At the collegiate level there are many relatively tall players, but most of them do not have the skill level of an NBA player. The best-of-the-best have often been NBA players who combine great height with high skill levels (e.g., Lebron James, Magic Johnson, and Kevin Garnett being examples; Michael Jordan, a few inches shorter than James, had greater skill, but he is close to the NBA median).

The article also highlights the fact that individual humans often want to attribute their own success to their hard work, or choices their parents made. Many of the players interviewed did not deny the importance of their size and athletic endowments, but emphasized the importance of learned work ethic and competition with family members of similar skill levels and physique. This illustrates two other aspects of quantitative genetics: gene-environment interaction and gene-environment correlation. Obviously these are real phenomena. But are they really relevant for an NBA player?

David Robinson grew up in a middle class family (his father was an engineer). He scored 1320 on the pre-recentered SAT (that puts his IQ well above two standard deviations) and majored in mathematics at the Naval Academy. Robinson’s non-basketball activities were, and are, copious (and not in a Dennis Rodman fashion).

He was not initially very good at basketball in secondary school, but underwent a massive growth spurt in his late teens. Eventually he became a standout basketball player at the collegiate level, and went on to a storied career (after serving some time in the navy). My point with recounting this is that even someone like David Robinson, who had many alternative paths, talents, and opportunities, and evinced no burning desire to become a basketball player at all costs, became a professional. Why? Because his raw talent was clear, and the reality is that becoming a professional basketball players is highly lucrative. The average NBA player earns millions. Even a washout player can earn millions in one year.

So we are at this point moving from the domain of quantitative genetics, to economics. Incentives matter. Millions of young people delude themselves into thinking they have a chance. The reality is that even someone like Jeff Hornacek, perhaps a mascot for those who argue that work ethic can match talent, is not physically typical (he’s 6’4). And, let’s be honest, work ethic matters a lot, but it too is heritable (mediated through conscientiousness). Wheels within wheels….

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