Where’d All the Possessions Go?

This post looks into the distant history. For a fun example of recent history myths, check out the NBA Geek, where Patrick shows how Charles Barkley has forgotten James Harden’s performance from a mere season ago. 

In my examination of scorers across time, a very common theme came up. Over time the game has “slowed down”. Back in 1974 when NBA first started keeping enough stats to track possessions, the average team had around 125 per game. Last season the NBA had simmered to only 105. That’s a lot of possessions that have disappeared in 40 years. The simple formula I’m using for possessions is

[Possessions] = [Field Goal Attempts] + 0.44 * [Free Throw Attempts] + [Turnovers]

The answer was a bit fun to look into.

Teams got more careful

turnovers_per_48

The biggest change that’s happened across times is that teams have been turning the ball over much less. In the 70s the average team would turn the ball over 20+ times a game. That’s dropped to around 14 in recent history. Around 25% of the change in possessions can simply be chalked up to better ball handling!

Teams got more careful, part two!

free_throws_per_48

From the mid-70s to the mid-80s teams just kept fouling. From it’s peak in 1987 though, teams have seen a pretty decent drop in fouling. A drop of around 8 free throw attempts a game has given teams about 4 possessions a game. It should be noted that teams have stayed pretty close to around 75% free throw shooting, so only the foul rate has had a real impact on possessions.

The Shortened Three and the Placebo Effect

three_pointers_per_48_minutesSince its inception in 1980 the rate of three pointers has steadily improved year by year. One of the most interesting changes to possession was 1995, when the NBA shortened the three point line. This resulted in a huge spike in threes, until the old distance was restored. However, teams have still kept up on three point shooting. Let’s examine another important aspect of that.

three_point_percentageNot only did teams start shooting more threes, they were getting better and better at them. The 1995 shortening saw a big boost in efficiency. However, even after the line went back to normal, teams were shooting threes at a 35%-37% rate, which is really close to the rate from 1995-1997. So maybe teams didn’t need a shortened three, maybe the magic was in them all along!

Teams got worse at getting the ball back

Teams used to get more second chances thanks to better offensive rebounds.

offensive_rebounds_per_48

And just to verify that this has been a decrease in teams actually getting the ball:

offensive_rebound_percentageTeams saw an improvement in offensive rebounds until the three point line came into existence. However, since then, teams have been getting worse and worse at getting back their misses. Let’s try and put all of these pieces together now.

Where’d they all go?

Now, the idea that teams have slowed down is certainly viable. However, it doesn’t tell the full story. In the past it was much more common for teams to just turn the ball over and foul. What’s more, teams were able to grab the ball back more easily. On the other side, teams have steadily increased the number of threes they take, while also getting more of them in the hoop. The 1995 season sped up this trend a bit, but it seems that teams have stayed on this track. Basically, possessions have gone down because teams have gotten better at not wasting them. A lot of the “lost” possessions from the past were simple wasted and bad possessions to begin with. The idea that basketball used to be better in the past, may not be as true as nostalgic fans want to believe.

-Dre

This was a fun project, but by no means a new idea. Open your copy of Basketball on Paper to Figure 3.1, which has a great chart by Dean Oliver, which also shows some good pop-outs including rule changes that impact pace and scoring.

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