Effective Height and Defending the Paint
By Josh Dhani
Written by Ian Levy
Last week, Tom Haberstroh had an excellent post at Hardwood Paroxysm, examining the relationship between a team’s collective height and their rebounding performance. He gathered the height measurements for each player and then weighted it by the minutes they played for their team. The result was a metric he calls “effective height.” Haberstroh found their to be a decent correlation (.33) between effective height and total rebounding percentage. When looking at rebounding by category there was almost no correlation (-0.03) between effective height and defensive rebounding percentage, but a reasonably strong correlation (0.42) between effective height and offensive rebounding percentage. It’s a terrific post and definitely worth a read.
I was really intrigued by his analysis, especially by the idea of effective height. I have been baffled recently by a few questions which seem related. One is, How do you predict which college players will become effective NBA shot blockers? The other is, How do you explain the Pacers being an average defensive team with an apparent lack of shot blocking, but still holding their opponents to the sixth lowest At Rim FG% in the league? I decided to use Haberstroh’s effective height data and compare it to three statistics. The first is each team’s block rate, or what percentage of an opponent’s shots they blocked. The second is At Rim FG%, or the FG% each team held their opponents to on shots at the rim. The third is Opponents At Rim%, or what percentage of an opponents shots were taken at the rim.
| Team | eHeight | BLKR | At Rim FG% | O At Rim% |
| SAC | 79.85 | 4.6 (24th) | 64.3% (27th) | 32.2% (12th) |
| TOR | 79.66 | 4.9 (22nd) | 60.3% (15th) | 32.6% (15th) |
| MEM | 79.47 | 5.0 (19th) | 62.5% (22nd) | 36.0% (28th) |
| PHO | 79.43 | 5.2 (15th) | 59.8% (11th) | 30.4% (8th) |
| CLE | 79.40 | 5.5 (9th) | 58.3% (7th) | 29.3% (2nd) |
| ATL | 79.36 | 5.4 (10th) | 60.7% (16th) | 33.7% (22nd) |
| OKC | 79.25 | 6.1 (1st) | 60.1% (13th) | 36.1% (29th) |
| NJN | 79.17 | 5.1 (17th) | 61.7% (20th) | 37.2% (30th) |
| MIN | 79.11 | 3.8 (28th) | 66.0% (30th) | 31.5% (10th) |
| LAL | 79.09 | 5.1 (16th) | 59.8% (10th) | 32.3% (13th) |
| LAC | 79.09 | 6.0 (3rd) | 61.7% (19th) | 33.2% (20th) |
| WAS | 79.04 | 5.4 (12th) | 65.9% (29th) | 29.1% (1st) |
| IND | 79.01 | 5.4 (11th) | 58.3% (6th) | 29.8% (5th) |
| POR | 78.99 | 4.7 (23rd) | 61.9% (21st) | 33.5% (21st) |
| UTH | 78.96 | 5.1 (18th) | 60.1% (14th) | 33.0% (17th) |
| DET | 78.95 | 4.2 (25th) | 62.8% (24th) | 33.1% (18th) |
| NYK | 78.95 | 3.8 (30th) | 63.5% (25th) | 34.2% (24th) |
| CHI | 78.87 | 6.0 (2nd) | 56.8% (1st) | 33.2% (19th) |
| ORL | 78.76 | 5.9 (5th) | 57.4% (2nd) | 29.4% (3rd) |
| DEN | 78.70 | 5.2 (14th) | 60.1% (12th) | 32.5% (14th) |
| DAL | 78.56 | 5.7 (7th) | 61.1% (17th) | 30.0% (7th) |
| SAS | 78.44 | 4.9 (21st) | 58.1% (5th) | 31.1% (9th) |
| CHA | 78.44 | 5.8 (6th) | 59.0% (9th) | 34.2% (25th) |
| NOR | 78.44 | 3.8 (29th) | 64.9% (28th) | 34.5% (26th) |
| PHI | 78.44 | 5.7 (8th) | 61.1% (18th) | 34.6% (27th) |
| MIL | 78.30 | 4.9 (20th) | 58.1% (4th) | 33.0% (16th) |
| MIA | 78.28 | 6.0 (4th) | 58.1% (3rd) | 29.8% (4th) |
| BOS | 78.25 | 5.2 (13th) | 58.5% (8th) | 29.9% (6th) |
| HOU | 78.21 | 4.0 (27th) | 62.7% (23rd) | 33.8% (23rd) |
| GSW | 77.91 | 4.0 (26th) | 64.3% (26th) | 31.6% (11th) |
| Average | 78.88 | 5.1 | 61.0% | 32.5% |
I was surprised to find in each case there was almost no correlation whatsoever.
- Correlation between eHeight and BLKR: 0.096
- Correlation between eHeight and At Rim FG%: 0.133
- Correlation between eHeight an O At Rim %: 0.128
Obviously, it takes more than height to defend the basket well. These numbers would seem to emphasize the importance of denying dribble penetration and challenging shots, even if you can’t block them. In the comments section of the Hardwood Paroxysm post someone mentioned the idea of calculating the effective height of just the front court players of each team, as having tall backcourt players can greatly increase a team’s effective height but may not make a difference in rebounding number,s since they spend much of their time away from the basket. Hopefully, I can crunch those effective height numbers for just frontcourt players soon and try running them against these three statistical categories. Perhaps we will see a stronger correlation. Stay tuned . . .