How to read Win Charts
Below I have some FAQs designed to make the NBA Win Charts I post easy to understand.
Q: What are “Win Charts”?
A Win Chart is my attempt to explain a team’s wins and losses to date by assigning responsibility for them to the participating players on that team based on each of the player’s minutes played and his marginal efficient production of the basketball statistics that correlate with wins. I’ve found them to be pretty reliable, but that doesn’t mean they’re absolutely bulletproof. I wouldn’t make that claim. The Win Charts are just meant to be an addition to the on-going conversation about who is valuable and who is not in the sport of basketball.
Q: What is Marginal Win Score?
Marginal Win Score is just an expression of each player’s statistical production per minute compared to the statistical production of the opponents who have played the same position at the same time. The measurement weights each of the statistics according to how its production correlates with winning basketball games (for instance, the number of points a player scores has no meaning in terms of his wins produced unless you also consider the number of possessions he used to score those points). For a much deeper background and explanation of MWS48, I have written a separate page.
Q: What are “Win__Loss Credits”?
Win__Loss credits are simply the number of team wins and losses I credit each player with producing based on his Marginal Win Score per 48 minutes and the number of minutes he has played.
Here’s how it works. First, I begin with the premise that every player is responsible for 1/5th of a game outcome (a win or a loss) for every 48 minutes he plays, which means each player is responsible for a full game outcome for every 240 minutes he plays.
Basketball games generally last 48 minutes. Each basketball team has five and only five players actively participating at any given moment during each of those 48 minutes. The outcome can only be based upon each active player’s comparative performance. Therefore every 48 minutes a player must be held accountable for 1/5th of an entire game’s outcome.
With that premise as my starting point, I calculate the number of wins the player can be credited with producing (using his MWS48, his minutes played, and then entering the two into the shorthand win production formula created by Professor David Berri). After I get the player’s win total, I get his loss total by dividing his minutes played by 240 and subtracting that result from his win total.
Q: What is “Win Contribution Index”?
Win Contribution Index is just a “value measurement”. It the product of a player’s Marginal Win Score per 48 multiplied by the percentage of the team’s total playing minutes that he used. Example: If LeBron James played 10% of the Cavaliers total minutes for whatever stretch of time I was examining, and his MWS was +6.50 over that stretch, then his Win Contribution Index number would be +0.650… a very, very good WCI.
What purpose does WCI serve? It allows me to compare any player’s value with any other player’s value over any given period of time… one game, ten games, a season, whatever.
Why not just use win credits for that? Because if you just use win credits you run into two problems.
The first is weighing his win production against his minutes. That’s often hard to determine without some kind of level playing field. WCI gives me that level playing field.
The second reason is over short periods of time, like one single game for instance, “win credits” devolve into confusing and somewhat meaningless integers. Win Contribution Index does not have that problem.
Q: What is “Player Win Average”?
Player Win Average is a “level of play” measurement. Basically it is the percentage of wins a player is generating for every 240 minutes he is on the floor. Don’t confuse it with a similar statistic used on 82games.com, though. On 82games, their “winning percentage” basically is the score of each game the player appears in while the player was on the floor. (So under 82games system if Charlie Bell is in for 5 minutes and the Bucks score 5 points during those minutes while the Bulls score only 4, Charlie Bell is credited with a “win” for that game).