With basketball season now upon us, it's time to have a little talk.
You might notice that when we write about basketball around here, we sometimes reference some obscure stats that you might not have ever heard of. "What the heck is efficiency?" you ask. Or perhaps you muse, "Turnover percentage? What is that, and why does it matter?" If you are among the uninitiated, then this post is for you.
First, if you're number phobic -- or have ever had your brain turned to scrambled eggs by baseball sabermetrics -- rest assured that these basketball statistics really aren't all that imposing and sound a heck of a lot more complicated than they really are. Although foreign to you now, most are pretty easy to compute (not that you'd ever have to compute them yourself), and, once you understand them, they all are pretty intuitive and easy to use.
Why do we reference these stats instead of more mainstream stats? Before we get to that, consider a common television talking head conversation that just gets my blood boiling every time:
Announcer A: Boy, you know the Cougars sure have a great defense, Jim!
Announcer B: You got that right, Pat! I mean, they truly are stellar -- they only give up 55 points per game! That is by far the best in Pac-10.
Announcer A: But talk about that Cougar offense a little. It's pretty solid, but hardly spectacular.
Announcer B: Yeah, you know Pat, (insert Cougar player here) is a pretty good player, and they shoot the ball at a pretty good clip as a team, but they only average 62 points per game -- worst in the conference. That WSU offense is hardly overwhelming.
Now, you might wonder why this irritates me so much. Keep that question -- and this announcer conversation -- in the back of your mind as we explore these superior statistics.
Why do traditional statistics suck?
Glad you asked. Most statistics look only at raw numbers -- how many points, rebounds, assists, etc. teams or players have accumulated. These are incredibly misleading. If two teams average 70 points per game, are both teams equally good offensively? How do you know? If a team scores under its average for the season, why did it happen? Is that something to be concerned about? That's what our advanced statistics, pioneered by the ideas of Dean Oliver and now calculated by Ken Pomeroy, measure better than anything else around.
Contrary to popular belief, the primary goal of basketball is not to score the most points. It's also not to accumulate the most rebounds or assists or steals, although that's what most traditional statistics imply. No, the actual primary goal of basketball is simple: At basketball's core, you're either trying to put the ball into the basket or trying to prevent your opponent from doing so. (Remember that. It will come up later.) In the process of doing each, you hope to have scored more points than your opponent when the clock hits 0:00.
When you shift your thinking this way, you realize that any competent statistic measure has to boil down to just that: How well did you do at converting each opportunity to score, and how well did you so preventing each of your opponent's opportunities to score? This is where the genius of Pomeroy and his statistics come into play, and reveal far more than traditional statistics could ever hope to.
A word about pace
The thing that most basic statistics overlook -- which is a colossal and completely debilitating oversight -- is pace. Pace is simply the number of possessions a team has in any given game. Any meaningful statistic must factor in that not every team averages the same number of possessions in a game. For example, WSU averaged just under 60 possessions per game last year. North Carolina, conversely, averaged close to 75. Comparing raw points scored per game -- or any other of the team's statistics -- is just not an apples to apples comparison.
This concept should come fairly naturally to Coug fans; after all, we've been watching WSU play at a slower pace than many of our Pac-10 counterparts for years now. So ...
POP QUIZ! Remember what I said above about the purpose of basketball? Ask yourself this question: Does the fact that the Cougars typically have fewer possessions in a game make them more or less good at scoring or preventing scoring than anyone else?
The answer is: Of course not. That's why traditional statistics suck.
So how do we level the playing field? It's simple, really. Since the goal of basketball is to score each time you bring the ball up the floor -- or prevent your opponent from doing so each time they bring the ball up the floor -- we need a statistic that measures how effective a team is at doing that. Efficiency wisely boils it down to possessions by calculating how many points a team scores per possession, then expresses that number in terms of how many points a team would score in a theoretical 100-possession game. Part of the beauty of that is that the national efficiency average generally is very near 100 -- 1 point per possession. (Of course, nobody plays 100 possession games, but doing it this way presents nice round numbers for our human brains.)
When we use efficiency, we gain tremendous insight into our team. For example, you intuitively know the Cougs have a great defense, and the statistics bear that out -- WSU had the 19th best defensive efficiency in the country last year. But what about the offense? Try this one on for size: With an offensive efficiency of 111.5, the Cougs actually had the 24th best offense in the country last year. Did you know that's practically the same offensive efficiency as another team announcers just drooled over for their "explosiveness" -- Tennessee? (The Vols checked in at 111.8.)
Now you know why that announcer conversation makes me want to throw something at my TV week after week. It's just a moronic, uninformed statement that could be rectified with just 15 minutes of research in the right place.
(By the way, if you explore Pomeroy and see "Raw Efficiency," that's how the team performed against its actual opponents. "Adjusted Efficiency" is simply an expression of how a team could be expected to perform against an average team on a neutral site.)
The Four Factors
Now the question becomes, What factors influence efficiency the most? While efficiency tells us whether a team is good with or without the ball in their hands, it doesn't tell us why. Oliver's research showed four things impact a team's offensive and defensive effectiveness above everything else: shooting the ball, retaining possession, creating extra possessions, and getting to the free throw line. There is a statistic to measure each, and I'll briefly explain each one:
Effective Field Goal Percentage (eFG%): This statistic measures how well a team shoots both 3-point and 2-point shots in one statistic. It's intuitive, because it gives a 3-pointer 1.5 times the weight in the percentage since it's worth 1.5 times the points. For reference, the national median in 2007-08 was 49.8 percent.
This is a great stat for Coug fans because no statistic bears a greater correlation to defensive efficiency than eFG% (in other words, the higher the eFG%, the higher the defensive efficiency, and higher defensive efficiency is, of course, bad). This makes sense because the WSU defense is predicated on keeping people out of the lane and making them shoot tough shots over you. If a team is hitting the 3's -- think about our difficulties with Oregon and Vandy in 2006-07 -- the vaunted Coug defense can be beaten.
Turnover Percentage (TO%): The percentage of possessions by a team that end in a turnover. It might seem obvious, but I'll point it out anyway: This is important because any possession that ends with a turnover ends without even the chance at scoring points -- a direct hit on the old efficiency. Obviously, you want this number lower on offense and higher on defense. For reference, the national median in 2007-08 was 20.8 percent.
Offensive Rebounding Percentage (OR%): The percentage of missed shots gathered in by the offense. Offensive rebounds result in increased possessions, which result in more chances to score points. Again, this is intuitive, but measuring how effective a team is at doing it in rate form, rather than raw accumulation form, is much more effective. For reference, the national median in 2007-08 was 32.8 percent.
Free Throw Rate (FTR): Of the four factors, this is the only one calculated differently for offense and defense. On offense, it's the team's ability to score from the free throw line, measured by free throws made divided by field goals attempted. On defense, it's free throws allowed divided by field goals attempted (since the defense has no control over whether an opponent makes his free throws). The national median for offensive FTR was 25.3 in 2007-08; for defensive FTR, it was 40.9.
If you want to see how the Cougs performed in each of these categories last year, click here. If you want more detail about how each of these are calculated -- like how do they come up with the number of possessions? -- Pomeroy offers more detailed explanations here and here.
Are there even more stats?
Of course there are, and you can explore them all to your hearts content at KenPom.com. (Highly encouraged.) We'll reference them occasionally, both in regards to the team and individuals. If you've got the hang of the ones I've explained, you'll get the hang of the others, too, without any problem.
For example, we'll often reference rebounding percentage with regards to Aron Baynes. When we talk about his defensive rebounding percentage, it's simply what percentage of his team's overall defensive rebound opportunities he's grabbing. When we talk about Taylor Rochestie's assist percentage, we're talking about what percentage of his team's assists he's dishing out. One key stat this year will be usage: What percentage of a team's possessions is a player personally responsible for ending? Another is offensive rating, which essentially combines shooting percentage, assists and turnovers into an individual offensive efficiency metric.
I hope you learn to love and use these stats, because they really do inform our opinions of our team as much as anything else, including simple observation. And if you really want to make yourself smart, make sure you stop by Basketball Prospectus occasionally and check out the writing of Pomeroy and John Gasaway. It'll improve your knowledge immensely.