Sunday, April 5, 2015

Detailed Per Possession Statistics now Available

Russell Westbrook fast break vs Arizona State 2008 What do last year's 76ers and this year's Warriors have in common? Certainly not offensive efficiency, where the Sixers ranked dead last in points per possession, compared to the Warriors' current #4 rank. The answer is pace. Over the past four NBA seasons, The Sixers and the Warriors are the only two teams to average less than 14 seconds per possession on offense.

Measures of pace and per possession efficiency, long a staple of advanced metrics, have historically been limited to what can be gleaned from the daily box score. In recent posts, I have attempted to extend the understanding of pace and efficiency by using detailed play by play data, rather than box score aggregations. For example, the Golden State Warriors have one of the league's slowest paces on defense, despite leading the NBA in overall tempo. And the Brooklyn Nets have a criminally low offensive efficiency for possessions that begin off of turnovers.

For those that want to do their own investigating, I have built a tool that aggregates pace and efficiency for both offense and defense: NBA Per Possession Statistics.

Data is currently available for the past four seasons, with plans to add more (play by play data goes all the way back to the 1996-97 season). League averages are at the bottom of the table. Here are average pace and efficiency numbers for the past four season, split by type of possession:

After Made Shot After Def Rebound After Turnover
season sec/poss pts/poss sec/poss pts/poss sec/poss pts/poss
2011-12 18.5 0.98 12.8 1.04 12.5 1.11
2012-13 18.4 0.99 12.7 1.05 12.3 1.13
2013-14 17.9 1.01 12.5 1.06 12.2 1.12
2014-15 17.9 1.01 12.6 1.04 12.2 1.12

The numbers are very consistent from season to season, with perhaps a slight trend towards faster pace and better offensive efficiency. Note that "After Turnover" includes both live ball and dead ball turnovers. As many have pointed out, there is probably a big difference between the two in terms of pace and efficiency. I have plans to split this out at some point, but for now they are aggregated.

Here are the fastest offensive teams of the past four seasons, and their corresponding offensive efficiency:

season team sec/poss pts/poss rank
2014-15 GSW 13.5 1.10 2
2013-14 PHI 13.7 0.98 30
2013-14 LAL 14.0 1.03 21
2013-14 DEN 14.0 1.04 16
2013-14 GSW 14.2 1.06 12

This year's Steve Kerr-coached Warrior team is the fastest offense of the past four seasons, but note that last year's Warriors cracked the top five with Mark Jackson at the helm. The Mike D'Antoni Lakers averaged just 14.0 seconds per offensive possession last season. That number has increased to 15.4 seconds this season under Byron Scott. Over the past four seasons, the Nuggets have been near the top of the league in offensive pace, perhaps in an attempt to use the thin Denver air to their advantage. And last year's 76ers were the embodiment of the ancient joke: "This food is terrible. And the portions so small". Philadelphia played at a blistering pace, but with little to show for it on the offensive end.

A technical note on the data: The per possession numbers are slightly lower than what you might find at basketball-reference.com. The main reason is that my code excludes technical free throws when subdividing a game into its component possessions.

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