Wins Produced and Statistical "Skepticism"

Because I'm stuck using a Mac for the time being, at the moment I have no idea how to make the nice images I like to include in my posts; in an effort to produce some meaningful content, I'm going to do a general post on Wins Produced and productivity in basketball.


Wins Produced (WP) is the best metric for evaluating NBA players. Don't just take my word for it; read all of these articles. But there will always be "skeptics", who, when presented with statistical evidence, proven predictive power, and the background theory behind WP, just can't let go of their "gut" feelings.

With that in mind, I'm going to try to explain the rationale behind WP. David Berri, Arturo Galletti,  Andres Alvarez, and others in the Wages of Wins network have largely appealed to the reality-based community and relied on statistical arguments in favour of WP; I'm going to forgo the numbers and deal mostly with words.


How to win in basketball

How do you win a basketball game? It seems obvious: all you have to do is score more than your opponent. That means that doing things that get you points are helpful, as are doing things that prevent your opponent from scoring. Things that you do that do not lead to points are not helpful, as are things that lead to your opponent scoring points. So here are the four major categories of actions in a basketball game:

1. Actions that help your team score points (positive outcome)
2. Actions that help your opponent score points (negative outcome)
3. Actions that prevent your opponent from scoring points (positive outcome)
4. Actions that prevent your team from scoring points (negative outcome)

And the three derivative categories:

1. Actions that both help your team score points and prevent your opponent from scoring points (double positive outcome)
2. Actions that both help your opponent score points and prevent your team from scoring points (double negative outcome)
3. Actions that don't fall into any of the above six categories (neutral outcome)

Now that we have that settled, it should be pretty easy to figure out which on-court actions help your team win. Here are some of the on-court actions that clearly belong in the first major category, "actions that help your team score points":

• Making a 2pt shot
• Making a 3pt shot
• Making a free-thow
• Getting an assist

These directly lead to your team scoring points; if you do any of these things, your team will have scored one or more points.


Here are some of the on-court actions that clearly belong in the second major category, "actions that help your opponent score points":

• Letting an opponent score points (ie: playing terrible defence)
• Fouling an opponent (leads to free-throws)
• Getting a technical foul (leads to free-throws)
• Goaltending
• Scoring on your own basket

It's pretty clear that doing any of these things leads to your opponent scoring; if you do any of these things, the opposing team will have scored one or more points.


Now for the on-court actions that belong in the third major category, "actions that prevent your opponent from scoring points". It's actually very hard to think of on-court actions that only belong in this category (if you can think of any more, leave me a comment):

• Preventing an opponent from scoring (ie: playing good defence)

You could probably make the argument that even this example doesn't truly belong solely in this one category.


Finally, the fourth major category, "actions that prevent your team from scoring points":

• Missing a 2pt shot
• Missing a 3pt shot
• Missing a free-thow

A shot missed is at least one or more points not scored.


Now we get into the three derivative categories, which I find much more interesting. Let's go over the positive one first, "actions that both help your team score points and prevent your opponent from scoring points":

• Grabbing an offensive rebound
• Grabbing a defensive rebound
• Stealing the ball from an opponent
• Forcing a turnover
• Drawing a charge
• Blocking the shot of an opponent
• Winning a jump-ball

All of these actions are things that gets your team possession; getting possession not only affords you more opportunities to score, but also prevents the opposing team from gaining possession (and thus prevents the opposing team from scoring as well).


Now let's look at the negative derivative category, "actions that both help your opponent score points and prevent your team from scoring points":

• Turning the ball over
• Getting an offensive foul
• Losing a jump-ball
• Allowing an opponent to get an offensive rebound
• Allowing an opponent to get a defensive rebound

Again, these are ways of losing possession. The last one is a bit contrived; teams generally rebound 70% - 75% of an opponent's misses, so "allowing" an opponent to get a defensive rebound is really to be expected.


Then we have the neutral derivative category, "actions that don't fall into any of the above six categories". This is another one that is hard to think up examples for:

• Winning an opening tip
• Losing an opening tip

Winning an opening tip means you gain the opening possession of the first and fourth quarters, but lose the opening possessions of the second and third quarters. Similarly, losing an opening tip means you lose the opening possession of the first and fourth quarters, but gain the opening possession of the second and third quarters. The net effect of either is neutral; the purpose of the opening tip is to start the game without giving an unfair advantage to either team.


To what degree?


Now that we know which actions do what, it's up to the stats experts to do analysis and come up with formulas that can determine to what degree each on-court action is responsible for winning. Unfortunately, some on-court actions - like quality of defence - are notoriously hard to determine. Stats experts have to rely on the only consistent and measurable on-court actions that exist for basketball - box score statistics. Yes, box score statistics can't measure all defensive contributions (remember, steals, turnovers, and blocks are all defensive measures that are a part of the standard box score), but they do measure some of the defensive contributions each player makes. So, using the standard box score stats, David Berri came up with Wins Produced (WP), which explains 95% of a team's wins. It's not perfect, no; but 95% is pretty damn good, and far more accurate than anything else out there. If you are interested in the methodology behind the specific way that WP determines productivity, I won't even try to give a detailed explanation - I'll just give you the links and let you have fun without me.

I hope that this post will help all you stats "skeptics" out there to reconsider your arguments. But, if that's not the case, I hope it was at least somewhat interesting.

- Devin.