David Biderman of the Wall Street Journal has a short story today on the aging of NBA players. The article notes that the peak age – or the point where player stop improving – is around 24 or 25 years of age. Biderman’s source for this story is some economist from Southern Utah University.
The research Biderman sites will be discussed in Stumbling on Wins (which should be shipped to bookstores in February or early March). Since everyone doesn’t have access to our book just yet (although we hope that changes for everyone – and we mean everyone – soon), let me offer a few observations.
Via a study of NBA players from 1977-78 to 2007-78 (a study discussed in more detail in the book), we found that an NBA player generally improves until he is in his mid-20s. Performance after this point is not much different until a player reaches about 27 or 28 years of age. After that point – and especially when a player passes the age of 30 – performance starts to decline more noticeably.
It’s important to note…
- we are reporting a tendency. The peak at 24 or 25 will not be true for every player. But when you look at the link between age and performance, controlling for a host of other factors, the general peak is in this range.
- the results were the same when we looked at NBA Efficiency. So this result does not depend on looking at performance via Wins Produced.
- the key issue is not the specific point in the player’s 20s where the peak occurs, but rather that performance after age 30 has a noticeable drop-off. In the player’s twenties the slope downward is quite gradual (and not something you would probably notice if you watched the player). In other words, LeBron will still be LeBron – barring injury – for a few more years.
Let me also add that the drop-off after age 30 will not be the same for everyone. For some players, performance declines considerably (as my post on Kareem and Shaq noted a few days ago). However, John Stockton posted a WP48 of 0.262 at the age of 40 (Stockton’s best season, though, was at the age of 25).
And one last note…JC Bradbury had a very interesting article on this subject in the context of baseball. One issue Bradbury emphasized is that more athletic activities (like tennis, short distance running, and swimming) tend to see peak performances at a very young age. In a sport like golf – and with respect to some aspects of baseball – peak performance occurs much later. Basketball is a sport that relies tremendously on athletic ability, so we shouldn’t be surprised to see a peak in the mid-twenties (as opposed to a point closer to 30 years of age).
Again, we have more on this in our next book (which you can already pre-order at Amazon.com).
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Our research on the NBA was summarized HERE.
Wins Produced, Win Score, and PAWSmin are also discussed in the following posts:
Finally, A Guide to Evaluating Models contains useful hints on how to interpret and evaluate statistical models.