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A lot of NBA players lie about their height. In the beginning of the 2019-20 NBA season, the NBA standardized how they measure player heights. Here are yearly height changes since the 1997-98 NBA season. This went from under 20 changes per year to about 250 in one season.
The average NBA height shrunk by about an inch. Below are the distributions for the last 11 years of NBA heights. Clearly, there exists a shift from being super-tall to merely...really-tall.
What the NBA has not standardized, though, are player weights. Here are the # of weight changes from year to year. While there is an increase in 2019-2020, it is not nearly as much as height.
Here is the distribution of reported NBA weights over the entire sample. These extra long bars are weights ending in 0s and 5s. While we do not have a way of seeing who is "lying" like we do for height, we might assume those with 0s of 5s are not accurately reporting.
Before I get into weights, I wanted to investigate the factors that led to players changing their heights. Were heavier players lying? Older players? Better players? I ran a regression (for the nerds: binomial w/ SE clustered by team) to predict who changed their heights.
To keep it simple, positive means more likely to change, and stars mean more likely to be a "true" effect. It appears that players who had a weight ending in either a 0 or 5 (~70% of the players) were much more likely to be lying about their heights.
While this is far from damning, we have moderate evidence that recording your weight as ending in a 0/5 may be a signal of a lie. Now, what characteristics are associated with players rounding off their weights? Using the full sample of player-seasons, here are the results.
The take away from this is that older, heavier players tend to round their weights. Also, once a player rounds their weight once, this sticks. Due to this, we can change the sample to look at only seasons where a player DID change. In other words, GIVEN a change, who rounds?
Here are the results. Older players round their weights. This probably has to do with information. You know what you're getting from veterans, but there is more uncertainty with younger players, so they need to send out more specific signals about themselves.
Here is a plot detailing the % of players rounding their weight at each age, and the number of players at each age. This non-rounding may be young players attempting to distinguish themselves from the pack.
Instead of just players, maybe teams have their hand in this too. Looking at which teams round the most, we see the Spurs topping the list with 92% of their player-seasons having a rounded weight. You might think, "this is a strategy!" but then the NYK come right after...
Here is a plot of each team's % rounded ordered by # rounded. Up until team #25, there seems to be a pretty flat slope. After 25, this starts to go a little crazy since these teams are changing names/cities. Regardless, this shows how far from "normal" SAS and NYK appear.
Given this table, this plot and the stark differences in the two leaders, I think we can safely say this is not strategic for teams. However, all this seems to point to younger NBA players trying to be as accurate as possible, since they are more likely to be "unproven".
One criticism might be that weights fluctuate over the course of an NBA season and this is all dumb. Fair. However, it's quarantine, and I'm allowed to read way too far into what players are saying about how heavy they are.
On the other hand, not rounding your weight may signal a level of "seriousness" which could play an important role when vying for a contract. Also, remember, players who didn't round their weights were also more likely to be telling the truth about their heights!
@ChrisVernonShow @KevinOConnorNBA you two might like to argue about how important it is, if at all, that NBA players may be lying about their weight and what it might mean
