The Heat stats glossary

February, 15, 2011
2/15/11
11:52
AM ET
By Tom Haberstroh
ESPN.com
Archive

Garrett W. Ellwood/NBAE/Getty Images
You have to consider the Heat's slow pace when sizing up the offense. Advanced stats can help.

I grew up memorizing the stats on the back of 1992-93 Fleer Ultra basketball cards. (As an aside, I still own pages of Shaquille O’Neal rookie cards, but sadly more Harold Miner ones.) As a little kid, I was drawn to statistics but I always had this nagging feeling that I wasn’t getting the full picture. I wanted more.

But when I grew up and finally got my hands on some new statistics, my excitement was quickly joined by anxiety.

What does this all mean?

So I read up on them. And it all kind of made sense. These “advanced” stats are grounded in solid basketball theory, not in abstract mathematics. It's worth keeping in mind that some advanced statistics are invented by analysts who played professional or collegiate ball and wanted to improve the way we look at the game.

If you're interested to learn more about the basketball metrics that analysts are using these days (including yours truly), here's a little handbook to use as a guide.

It's a stats glossary through the lens of the Miami Heat.

Offensive and Defensive Efficiency

What is it? The number of points a team scores/allows every 100 possessions.
Why do you need it? Because points per game has trouble rating super slow or super fast teams.
Who cares? The team.
Where you can find it? Hollinger’s Team Statistics.

Let’s start from the top. The Heat score 101.7 points per game, which is good for 10th in the NBA. But that lofty ranking actually underrates the Heat’s ability to score.

Why?

The Heat play at a slow pace. They stretch out their possessions and force teams to use every second on the shot clock. As a result, the longer possessions lead to the Heat enjoying fewer opportunities to score during a 48 minute game. On the flip side, a team that plays quickly has more opportunities to score during those 48 minutes.

Those extra opportunities are important. When we grade an offense, what we’re really doing is evaluating its ability to score with its opportunities. And each possession is an opportunity to score. You can think of possessions as the currency of basketball.

The Heat score approximately 1.088 points per possession. That's an unwieldy figure -- seriously, no one likes going out to three decimal places -- so we like to scale it by multiplying it by 100. How’s this? the Heat score 108.8 points every 100 possessions. That’s the Heat’s offensive efficiency, which measures their ability to produce on offense. (It’s also referred to as a team’s offensive rating).

How good is an offensive efficiency of 108.8 points per 100 possessions? Well, looking at the leaderboard, we find it ranks fourth in the NBA, just behind Denver (110.0), San Antonio (109.1) and Los Angeles (108.9). The Heat leap-frogged six teams going from “per game” to “per possession” once we account for speed.

But we need to adjust for pace on both ends of the floor, not just offense. The Heat allow 99.5 points per 100 possessions defensively, which ranks third in the NBA behind Chicago (97.1) and Boston (97.6).

Effective Field Goal Percentage

What is it? A player’s shooting percentage after accounting for the added bonus of a 3-pointer.
Why do you need it? Because not all field goal attempts are created equal.
Who cares? Good 3-point shooters such as James Jones, Eddie House and Mike Miller.
Where you can find it? Basketball Reference, Hoopdata.

Issac Baldizon/Getty Images/NBAE/Getty
3-point shooters such as Eddie House get a nice bump from effective field goal percentage.

Against Indiana last week, Jones shot 2-for-6 from the floor -- 33.3 percent. Using the standard of plain ol’ field goal percentage, that’s not a good shooting night.

But any coach would be happy with that performance, and it’s easy to see why. Jones' two makes were from beyond the arc, netting the team six points on six attempts from the floor. It’s the equivalent of someone shooting 3-for-6 from 2-point land.

We know 3-point shots are worth more than 2-point shots, but we miss that valuable piece of information when we cite field goal percentage. As a result, 3-point shooters tend to be undervalued by traditional shooting measures.

Jones has an unsightly 42.1 “shooting” percentage, but would you call him a bad shooter? Of course not. Once we incorporate the added bonus of a 3-point shot, we find that he’s effectively shooting 60.0 percent from the floor. For someone who does nothing but shoot 3-pointers, that’s a subtle but critical tweak in evaluation. How good is Jones' eFG%? Head over to Hoopdata.com, the indispensable resource and newcomer to the TrueHoop Network co-founded by Joe Treutlein. Choose the relevant qualifiers and you'll see that James Jones has the highest eFG% of any regular swingman (minimum 20 minutes per game).

For reference, House has a 56.5 effective field goal percentage and Miller checks out at 52.7.

True Shooting Percentage

What is it? A player’s shooting percentage after accounting for free throws and 3-point shooting.
Why do you need it? Because free throw shooting is still shooting.
Who cares? Those who frequent high-efficiency areas -- free throw line and 3-point line (LeBron James and Dwyane Wade).
Where you can find it? Hollinger’s Player Statistics, Hoopdata.

True shooting percentage improves on the field goal percentage model just as effective field goal percentage does, but it takes it one step further: It includes free throws.

It’s a little trickier to compute, but true shooting percentage essentially tells us how efficient a scorer is when he shoots the ball. Since a lot of a player’s value comes from his ability to get freebies at the line, we should capture that in a shooting percentage. And that’s where true shooting percentage comes in.

Here’s a little example. Way back in mid-December, James shot 9-for-19 from the floor against the Wizards, but his shooting percentage (re: field goal percentage) didn’t do his night justice. He shot pretty well from downtown, nailing 3 of 7 3-point field goal attempts and making 11 of 12 free throws. Yeah, he only made 47.4 percent of his field goal attempts, but his scoring impact and efficiency were far greater than his traditional shooting percentage suggested. His true shooting percentage -- TS% for short – was 65.9 percent on the night.

In summary, field goal percentage is acceptable as an accounting figure. There’s nothing wrong with saying that a player went 6-for-13 from the field. But as soon as we start attaching evaluation solely based on that figure, it becomes an issue. A player can have a good shooting night, or be a good scorer, even if he doesn’t wield a shiny field goal percentage.

Pace Factor

What is it? The number of possessions a team uses per game.
Why do you need it? Because speed disrupts our evaluations.
Who cares? Methodical, slower-paced teams.
Where can I find it? Hollinger team stats pages.

The Minnesota Timberwolves have scored 102.3 points per game this season, which means, as a team, they have scored more per game than the Heat this season.

Would you say the Timberwolves are a better offense than the Heat?

Here's why you shouldn't: The Timberwolves' better standing in points per game is a testament to their speed of play, not their quality of play. Minnesota is the fastest team in the NBA, notching an average of 99.6 possessions per game. It takes the first look it sees then gives the ball back to the other team and does it all over again. On the other end of the spectrum, the Heat average just 93.2 possessions per game, which means that their games are effectively 6.4 possessions shorter than the Timberwolves. In other words, the Timberwolves, on average, get about six more opportunities to score than the Miami Heat on a game-to-game basis.

When we level the playing field, we see that the Timberwolves ability to score buckets is vastly overrated by points per game and the Heat are far better with their scoring opportunities. Minnesota scores 101.8 points per 100 possessions, which is a full seven points fewer than the Heat's rate of 108.8. That, my friends, is the illusory power of speed. The Heat are more methodical getting their points, whereas the Timberwolves impulsively shoot to cover up their deficiencies.

Usage Rate

What is it? The estimated percentage of team possessions a player uses while on the floor.
Why do you need it? Because ball hogs need to be outed.
Who cares? James, Wade, Chris Bosh and Joel Anthony.
Where you can find it? Basketball-Reference.

Did you wonder how the Big Three were going to share one ball this season? Well, usage rate is your statistic.

Usage rate combines all possession-ending actions (field goal attempts, free throw attempts and turnovers) to evaluate a player’s share of scoring responsibility. Hypothetically speaking, if every player in a lineup shared the ball equally, each individual’s usage rate would be 20 percent, which should give a round benchmark for reference. Most role players sit below that 20 percent line and franchise players far exceed it.

The Heat are fascinating in multiple respects when it comes to usage rate. Let’s start with Wade. Everyone would agree that Wade shouldered an enormous scoring burden for the Heat when O’Neal left Miami. And usage rate captures that. In 2008-09, Wade “used” 36.2 percent of the Heat’s possessions while on the floor, which was tops in the league. He led the league again in usage rate last season, with a 34.9 percent mark.

When James and Chris Bosh came into town, that number was sure to drop. And it did. Now, Wade only uses 31.6 percent of the Heat’s possessions while on the floor, down 3.3 percentage points from last season.

But the world wants to know who the alpha dog is on this team. Is it LeBron or Wade? If you pick usage rate as the measuring stick, LeBron has him beat -- by a hair. LeBron’s usage rate in Miami is 32.0 percent, just a tad higher than Wade’s 31.6 percent. But that has been seesawing back and forth all season. Interestingly enough, James’ usage rate has ticked down only 1.5 percentage points since last season, from 33.5 percent to 32.0 percent, slightly less than Wade's drop-off.

You know how everyone talks about the Big Three’s sacrifices after joining the Heat? No one has sacrificed more than Bosh. After enjoying 28.6 percent of Toronto’s offense last season -- a colossal mark for someone who doesn’t have ballhandling duties -- Bosh has seen his usage rate plummet this season next to LeBron and Wade. This season, he’s only using 23.6 percent of the Heat’s possessions, which is more than three times the cut LeBron has seen.

No one outside the Big Three has a usage rate above 20 percent for the Heat this season, which makes sense considering how frequently the offense goes through that trio. If you want to see something astounding, check out Anthony’s usage rate. It sits at a microscopic 4.8 percent, the lowest scoring responsibility for an NBA regular (averages 20 minutes per game) in the history of the NBA. You know how people say the game turns into 4-on-5 when the Heat have Anthony on the floor? That’s what they’re talking about.

Keep an eye on usage rates as we head into the playoffs. Will the scoring responsibilities shift as the stakes grow higher? Who will end up with the usage rate title belt when it’s all said and done?

Rebound Rate

What is it? The estimated percentage of available rebounds a player/team collects.
Why do you need it? Because rebounding margin is flawed and per game numbers aren’t enough.
Who cares? Mike Miller.
Where you can find it? Hollinger’s Player Statistics.

If you’ve noticed that you’re hearing the term "rebound rate" more often these days, there’s good reason or it. Like many other advanced stats, rebound rate (sometimes called total rebound percentage) is a great equalizer for bench players whose playing time affects their per game numbers.

Take Miller, for instance.

At 5.1 rebounds per game, Miller trails LeBron (7.3) and Wade (6.8) in the rebounding column, but that order has more to do with playing time than anything else. Miller has been a far better rebounder, but his 19.5 minutes per game drag on his per game figures.

You’ll see Miller’s superiority in rebounding by looking at his rebound rate, which is 15.3 percent this season -- meaning Miller collects an estimated 15.3 percent of available rebounds while on the floor. Miller’s mark of 15.3 percent outpaces LeBron (11.1), Wade (10.6) and even, yes, Bosh (13.2).

Rebound rate cuts straight to the point. There’s no need to adjust for playing time. And perhaps more importantly, there’s no need to adjust for how well teams are shooting. This is another advantage that rebound rate enjoys over using traditional rebounding numbers. Sometimes teams shoot lights-out and a player simply doesn’t have many rebounds available to him. Rebound rate estimates how many available rebounds a player sees on the floor and how many of those he collects.

Rebound rate also gives us another tool in storytelling. Remember when Zydrunas Ilgauskas tallied nine offensive rebounds against the Cavaliers a few weeks ago? To put that into context, Ilgauskas’ offensive rebound rate was an astronomical 57.1 percent, which means he collected over half of the Heat’s missed shots while he was in the game. Sure, nine offensive rebounds sounds like quite an achievement, but when you phrase it in the terms of rebound rate, it makes his rebounding performance far more impressive.

Plus-Minus

What is it? The team’s scoring margin when a player is on the floor.
Why do you need it? Because the box score doesn’t tell you everything.
Who cares? Bosh.
Where you can find it? Basketballvalue.com.

Plus-minus is probably the hottest advanced statistic out there. And while it offers new insight on a player’s contributions, there are some limitations.

With Udonis Haslem injured, the Heat are pretty thin behind Bosh. When he leaves the game, it usually means that a Heat player has to play out of position (LeBron) or that Juwan Howard is in the game. As a result, the Heat don’t do nearly as well when Bosh sits out.

But how bad is it? Pop over to Bosh’s Basketballvalue.com player page and you'll find that the Heat have outscored opponents 3,827 to 3,438 while Bosh has been on the floor this season, which gives him a plus-minus of plus-389 on the season. When he’s off the court, the Heat only outscore teams by plus-34 points (1,667-1,633). Big difference right?

Yes, but we can learn more about Bosh’s impact once we translate plus-minus into offensive and defensive efficiencies. Again, on the Basketballvalue.com player page, we find that the Heat score 112.8 points per 100 possessions with Bosh on the floor, but when he falls out of the lineup that figure drops to 107.0 points per 100 possessions -- a 5.8 point net difference. And defensively, the Heat allow 1.2 fewer points per 100 possessions while he’s on court (remember, like golf, allowing fewer points on defense is a good thing).

So Bosh's net point differential is plus-7 points per 100 possessions (5.8 plus 1.2). Net point differential sounds scary but it answers the question what is a player’s plus-minus on a per possession basis?

On-court/off-court numbers are making their rounds in analysis circles because it shines light on the dark areas of the box score. Erik Spoelstra often says Anthony makes an impact on defense that can’t be captured in a box score (namely, pick-and-roll coverage), and we see in plus-minus numbers that the coach is onto something. The Heat allow 0.6 fewer point per 100 possessions when Anthony is in the game. A small figure, but it lends some credence to Spoelstra’s words.

You can refer to plus-minus in box scores, too. In the ESPN.com box score, there’s a column that shows a player’s plus-minus figure in a particular game. For instance, in the loss against Boston on Sunday, Miller posted a minus-11 figure, which means that the Heat were outscored by 11 points with the sharpshooter on the floor.

Be careful drawing conclusions in single-game plus-minus. Correlation does not indicate causation. Against Boston, Anthony posted a plus-5 figure but he could have just benefited from being on the court during a Heat run that he had little to do with. Just like any other statistic, plus-minus is not the end-all-be-all and shouldn’t be treated as such.