In the comments for the previous post on Measuring the Quality of Basketball in the NBA Commenter Dan said:
“I don’t think this kind of analysis makes sense. What you’re calling higher average team productivity probably just reflects factors like a faster leaguewide pace, higher scoring per possession, and maybe trends in some specific statistics. A faster pace allows players to accumulate more statistics, so it’ll lead to higher pre-adjustment WP. With many statistics the two teams’ change in WP cancels out (e.g., a steal for one team is a turnover for the other, a defensive rebound requires a missed shot), but not with scoring, so more offense will increase pre-adjustment WP. The 1990s saw a drop in both pace and points per possession, so that explains the drop in “basketball quality.””
Huh. He’s right. I did not think to adjust for pace when I did the Analysis. But to paraphrase the immortal words of Herm Edwards : “We can definitely build on this”
Calculating Pace in the NBA
To calculate pace in the NBA we need to estimate the number of possesions per game in the NBA. In the world of Wins Produced (and really in the world of basketball) possession of the ball is currency and what you do with it is what determines whether you win or lose. To quote another sage: “Ball don’t Lie”. So for any truly comparative measure of true basketball productivity and quality (our value delivered) adjusting for the possessions (our spend) is critical.
How do we calculate the number of possessions? A standard formula used is:
Possessions = .96 * (FGA − ORb + TO + (.44 * FTA)) (source)
If we calculate possessions per game since 1978 looks like this:
So the pace of the NBA slowed significantly and at a consistent rate from 1978 (210 poss. a game) to a low of 174.5 poss a game in 1999 before picking back up to about 180 possession per game (90 per team) since. With this information we can now adjust or quality measure accordingly.
Average Player Productivity
Some adjustments to the numbers from the previous post before we get to pace. As noted I was calculating average Team productivity per 48 minutes played based on simply adding the average production (ADJP48 click here for detail) for all 5 position (Center,Power Forward, Small Forward, Shooting Guard &Point Guard). It occured to me that the number would look more in line to typical Position Adjustment numbers for calculating WP48 if I divided by five. So I did, Here’s the new table:
Pace Adjusted Quality in the NBA
So we have pace and average productivity per player, let’s put them together shall we.
For the purpose of this exercise we will calculate :
Productivity per 200 possesions = (Avg Player Productivity per Game (ADJP48)/Avg Number of Possessions per Game)*200
In table form this looks like:
So once we adjust for pace, we see that we get a very different picture. 1991 thru 1997 was a golden era but the last three Years have actually been better for quality than anything in the data set. The dip in 1999 and the early 2000’s remains . Post Merger basketball looks worse . I guess our memories can lead to view the past thru rose-tinted glasses.
A few notes before the end:
- I realize that the introduction of the three point shot to the league in 1980 skews the early numbers and the 95to 97 short three point line skews it as well. C’est la vie. I figure some sort of adjustment around the % of FGA that are 3PA is needed. Looks like something for take 3
- Ditto for the handcheck rule. Need to think about this one.
- The point of this exercise is to establish a way to compare historical performance by teams over time. Please hit me with questions and doubts so that I can help this puppy grow into a nice strong big dog.
To Guy in the Comments:
What I’m doing is closer to:
PROD = 2FGM*0.032 + FTM*0.017 + FGMS*-0.032 + FTMS*-0.015 + REBO*0.032 + REBD*0.033 + TO*-0.032 + STL*0.033 + FTM(opp.)*-0.017 + BLK*0.019 + AST*0.022
Than Pts per possesion. Pts per possesion looks like this :