Nylon Calculus: LeBron James and the slam dunk aging curve

LeBron James is a statistical outlier in so many ways, including the fact that he’s still a dunking machine at 38 years old.

Whether it’s Michael Jordan soaring gracefully through the air, tongue wagging, or Ja Morant trying to obliterate a defender into their component atoms, the dunk is undoubtedly the most visually appealing play in basketball for casual fans and hardcore viewers alike. Not only must a dunker combat the world’s largest humans, but they have to fight gravity itself to demolish a metal ring located 10 feet off the ground — far above the reach of most of us.

Dunks are generally a younger person’s game. The lift, strength, and aggressiveness required all tilt toward people in their physical prime. But not all basketball players are created equal. This year, we’ve watched 38-year-old LeBron James rampage his way to the rack for one slam after another in his quest to become the NBA’s all-time leading scorer.

I wanted to take a closer look at how often he and others are dunking as they get older. What does the dunk aging curve look like for players? Luckily, Basketball-Reference has detailed dunk notes for every NBA player dating back to the 1997 season, so I collated all the seasons from 1996-1997 up through Jan. 31 of the 2022-2023 season to investigate further.

To set the scene, let’s look at dunk attempts as a percentage of field goal attempts (FGA) by season:

That’s nifty! Dunks were pretty steady at roughly 5 percent of total field goal attempts for a long time, but they’ve been on the rise since the mid-2010s. The increased emphasis on spacing in the modern era makes for fewer obstacles in the lane. When a driver can beat his man, it’s easier than it used to be to rise unimpeded for a jam.

Now that we’ve established a baseline, let’s see what happens to players as they age. I’ve split by position to account for the fact that greater height generally leads to more dunks*. Sample sizes at the tail end tend to diminish rapidly, leading to some notable outliers, but there are still clear trends:

Wow! Every position dunks the most, as a percentage of field goal attempts, during rookie seasons (outside of LeBron-driven weirdness). I had been expecting a short ramp-up since most NBA players put on muscle in their first few years in the league, and I assumed that added strength would lead to more dunks. But there is a slow and steady decline from the first year that is only arrested in the late teens, when sample sizes become just a handful of players.

In fact, LeBron alone is responsible for the two strangest positional spikes — the point guard boost in years 17-18 and the power forward spike in years 19-20 (Basketball-Reference changed his position in those years). There are so few players who play that long that a still-prolific dunker like LeBron can single-handedly dominate the positional averages. For example, there have only been three players listed as power forwards to make it 20 years in the league since 1997: LeBron James, Kevin Garnett, and Udonis Haslem. And let’s just say that UD isn’t exactly over-weighted in the dunking sample here. More on LeBron shortly.

Taking a step back, we knew that position would be heavily correlated to dunk frequency, but I didn’t expect it to look so clean. It’s incredible how perfect the splits are by positional designation, like some sort of natural law unveiled.

Interestingly, the center dunk decrease, on a relative basis, isn’t as steep as at the other positions. Given the emphasis on rim-running and the decline in post players, it makes sense that centers stay dunkin’ as they age. Even older 7-footers can dunk without much physical trouble, and they are already close to the basket. Moreover, as the NBA becomes more and more perimeter-oriented, few offenses give their centers many field goal opportunities that aren’t dunks or layups.

On the other hand, point guards stop dunking after year four. Dunks never crack one percent of field goal attempts again, except for those two LeBron-driven anomalous years. In this database, no other point guard with at least 16 years of experience has even attempted a dunk in a game except Lou Williams, who had one jam in his 17th and final year. Here it is, for your viewing pleasure:

Pretty good for a guy who didn’t even try a dunk the year prior!

When we examine the dunk aging curve by actual player age instead of years of experience, we see essentially the same pattern:

(Shoutout to Dikembe Mutombo, dunking machine at the age of 41.)

Point guards and centers do have a bit of a ramp-up here, but in general, it’s the same pattern as we saw above.

I also examined this on a dunks-per-minute basis, regardless of shot selection, and saw similar trends.

This downward slope with age generally holds true for even the most famous dunkers, with one notable exception — LeBron James

We’ve already seen LeBron changing the aging curve all by himself, but looking at his entire dunk aging curve reveals what an anomaly he really is:

In year 20, LeBron is somehow dunking more frequently than he did as a rookie. Mind-boggling.

But maybe LeBron isn’t unique; perhaps other superstars with absurd athleticism have some Benjamin Button built into them. So I checked against a handful of prominent players. Is this true for other famous superstar dunkers? In a word: no.

Some takeaways:

I miss young Blake Griffin (white line). I appreciated his ability to adapt and evolve as he got older, when he became a far more complete player. But early Blake was dunking 20% of his shot attempts, more than most centers, and they were some of the best in-game dunks of all time:

https://twitter.com/SportsCenter/status/1197221878341013504

And that wasn’t even his best dunk that game! Sigh.

Kevin Durant (black line) was on a similar trajectory as LeBron, but the Achilles injury seemingly took away his explosion. Luckily, his midrange is nearly as efficient as most players’ slams, so it hasn’t hurt much. The best superstars can make up for declining athleticism with improved skill.

Vince Carter and Russell Westbrook are perfect examples of what happens to most players over time — an uneven but steady downward trend as they lose a half-step.

Looking at someone younger, Ja Morant is already on the downswing, although he’s still dunking at small forward levels despite standing 6-feet-2-inches on a good day. We now know that Year 4 tends to be the last hurrah for the average point guard dunker, but Ja will hopefully age far more gracefully than most; at the least, he’s starting from a higher vantage point.

There are many reasons players dunk less often over time

There are plenty of reasons why dunks decline over time, and most will be obvious. Men typically peak physically in their mid-20s. After that, it often becomes harder to generate the same lift. Your average player becomes more skilled and gains more trust in their jumper with age, so they settle for more outside shots rather than attacking the paint.

Players accrue injuries that sap their athleticism. Simultaneously, many people become more injury-averse as they get older (since older players generally have a harder time recovering from injuries and are a little more cognizant of their impending basketball mortality), which may cause them to approach the rim more trepidatiously.

A few may lose confidence in their free-throw shooting with age, leading to less aggression. Offensive roles change frequently, and defenses become more familiar with players’ athleticism and attack habits. And, of course, some simply choose to take it easy on their aching knees by jumping for layups instead.

As former NBA player Jamal Crawford once told Bleacher Report:

“It’s only so long a guy who is dunking can do that, so you have to eventually think about preservation,” said 17-year vet Jamal Crawford… “I would trade that for longevity because you only have so many dunks in your legs.”

Regardless of the reason, the vast majority of players succumb to gravity as their career extends. In this, as in so many things, LeBron remains a physical outlier.

*Basketball-Reference can have funky positional designations. For example, LeBron bounces between SF, PF, and PG depending on the year. If players are listed as split positions (e.g., PF-SF), I put them as whichever position was listed first. Since we’re talking data, one other caveat: years of experience refers to how many years a player has played a minute of basketball. It omits entire seasons that were missed due to injury.

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