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Advanced statistics in basketball

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APBRmetrics is the analysis of basketball through objective evidence, especially basketball statistics. APBRmetrics is a cousin to the study of baseball statistics, known as Sabermetrics, and similarly takes its name from the acronym APBR, which stands for the Association for Professional Basketball Research. The phrase may be awkward (just think basketball metrics or basketball measurements) but the work being done is giving teams and fans more and better tools to understand what is happening in the game of hoops.

A key tenet for many modern basketball analysts is that basketball is best evaluated at the level of possessions. During a single game, both teams have approximately the same number of possessions, because they alternate possession. (A team can have slightly more if it begins and ends a quarter or half with possession.) However, over the course of the season, teams play at very different paces, which can dramatically color their Points Scored and Points Allowed Per Game. Therefore, these analysts favor use of Points Scored per 100 possessions and Points Allowed per 100 possessions.

A second core tenet is that per-minute statistics are more useful for evaluating players than per-game statistics. From John Hollinger's Pro Basketball Forecast:

"It's a pretty simple concept, but one that has largely escaped most NBA front offices: The idea that what a player does on a per-minute basis is far more important than his per-game stats. The latter tend to be influenced more by playing time than by quality of play, yet remain the most common metric of player performance."

Hollinger's assertion has been borne out by the fact that, in most cases, players who receive increases in playing time continue to play with the same effectiveness that they did in fewer minutes. To wit: based on their per-minute numbers, Hollinger accurately projected Michael Redd and Zach Randolph (among others) to become stars when they finally received significant minutes from their teams. Finding such players, a long-time pursuit of hobbyists, now got more public recognition, including from some NBA teams.

History

While the use of possession stats dates back at least as far as former North Carolina Coach Frank McGuire, modern APBRmetrics came into existence when Bill James gained popularity for his Baseball Abstracts and basketball enthusiasts borrowed some of the ideas and the overall philosophy of the importance of statistical analysis for finetuning achievement. Early APBRmetricians focused on "linear weights" statistics, which assign a value to each key statistic and add and subtract to find a player's total efficiency, usually on a per-minute basis and various brands of this were created and often became the basis for books.

Beginning in the 1990s, Dean Oliver popularized the use of possession statistics. Oliver and John Hollinger are credited with moving the use of basketball statistics forward to this next level and into the view of more basketball fans in the early 2000s. Oliver published his book Basketball On Paper in 2003, while Hollinger began writing the Pro Basketball Forecast series in 2002.

Several dozen other serious basketball fans / analysts also make regular and helpful contributions to finetuning the methods and their usage and advancing new approaches to research questions through the active internet forum including, to name 2 examples, the very statistically adept Ed K. and Mike G., the creator of the EWins method for evaluating the importance of player contributions to winning.

In the wake of the best-selling book Moneyball, which glamorized Sabermetrics, APBRmetric approaches began to receive evem more attention from the media and NBA teams. The goal was not just to find productive players but to find the most productive mix of players within the salary cap or budget.

In 2004, Oliver was hired as a full-time consultant by the Seattle SuperSonics, making him the first APBRmetrician to be employed by an NBA team full-time.

The Houston Rockets took the movement one step further in April 2006 by hiring Daryl Morey as their assistant general manager and announcing that he would replace Carroll Dawson as general manager after the 2006-07 season. Morey, previously Senior Vice President of Operations and Information for the Boston Celtics, had provided statistical analysis for the Celtics front office and wrote about advanced statistics for the Celtics Web site but had no traditional basketball experience as a player, coach or scout.

The website 82games.com, which debuted in 2003, brought the analysis of plus-minus ratings -- how well a team fares with a certain player or lineup on the floor as opposed to on the bench -- and counterpart production into the mainstream. There is also more detail on shooting effectiveness by location on the court and time on clock. These statistics allow APBRmetricians to measure contributions not accounted for by traditional statistics, particularly at the defensive end of the court, an area underdeveloped in the first wave of new stats including PER and the initial player points allowed defensive rating (which was not based on play by play tracking of one on one defense because it was not yet available and also gave heavy weight to points allowed by the rest of the team as well as the player himself. Some now prefer the counterpart and team measures of defense at 82games which are based on writtten play by play records but arent perfect either.)

A new site linking video on demand with statistics is expected soon.

Prominent APBRmetricians / Modern Basketball Analysts and Data Providers

Roland Beech is the proprietor of 82games.com and has contributed his analysis to ESPN.com and SportsIllustrated.com.

Bob Bellotti was one of the first APBRmetricians, having invented "Points Created," a player rating system that attempted to boil all of a player's contributions into one number (similar to Bill James' Runs created). He is currently the most widely used statistical consultant to NBA teams. Bellotti wrote several books in the late 1980s and early 1990s, and contributed to the NBA's official encyclopedia, Total Basketball.

Bob Chaikin used APBRmetric principles to create a basketball simulation called Bball. Chaikin's simulation can simulate hundreds of games in minutes to assess the impact of various lineup and rotation changes or the value of a player. It has been used by several NBA teams. He offers it and a historical database at his website.

David Berri is a professor of economics at Cal State-Bakersfield, and his contribution to APBRmetrics is a 1999 research paper entitled "Who is 'Most Valuable'? Measuring the Player's Production of Wins in the National Basketball Association". The paper introduced economic principles into the player rating process. A new book is forthcoming in 2006.

Dave Heeren wrote a series of Basketball Abstract books in the early 1990s and invented the most prominent early rating system, TENDEX.

John Hollinger is the author of the Pro Basketball Forecast/Prospectus series and a regular columnist for ESPN Insider. Hollinger's work is read by many mainstream fans who are not familiar with APBRmetrics in general, making him instrumental in introducing advanced statistical concepts to regular NBA fans.

Dean Oliver is a consultant for the Seattle SuperSonics and author of Basketball on Paper, and is widely recognized as a main leader of the APBRmetrics movement. His research into the importance of pace and possessions, how teamwork affects individual statistics, defensive statistics, and the importance of a player's ability to create their own shot has been groundbreaking. His highlighting of the 4 Factors (field goal shooting, offensive rebounds, turnovers and the rate a team or player get free throws) also help provide a useful framework for evaluation of players and teams.

Kevin Pelton is a sportswriter who covers the Seattle SuperSonics and Seattle Storm for their respective websites. Also a writer with 82games and CourtsideTimes.net, Pelton has worked to get mainstream basketball fans acquainted with statistical analysis and also hosts the APBR forum site.

Dan Rosenbaum is a consultant for an NBA team. Rosenbaum's work has focused on adjusted plus-minus ratings, which take into account the players playing with and against a player and adjusted his plus-minus accordingly to overcome the uneven playingfield of unadjusted stats where some players have stronger teammates on thefloor with them than others and play more or less against staters vs. substitutes.

Jeff Sagarin and Wayne Winston pioneered adjusted plus-minus statistics with their WINVAL system, which has been used extensively by the Dallas Mavericks.

Justin Kubatko developed and administers basketball-reference.com providing much relied upon and easy access to many of the advanced basketball statistics, much of which is not available anywhere else for seasons before the most recent few years.

Common statistics

Among the growing list of advanced basketball statistics here are some of the most important ones gaining increased usage:

Offensive Rating/Offensive Efficiency and Defensive Rating/Defensive Efficiency, on a team level, are calculated as Points Scored and Points Allowed per 100 possessions. Possessions are usually estimated by the following formula:

The .44 accounts for the fact that when a player scores a basket and is fouled, they shoot a free throw, which is not a possession. This is also true of flagrant fouls and technical fouls, while three free throws make up one possession when a player is fouled shooting a 3-pointer. It should also be noted that when analyzing College Basketball, APBRmetricians have used .475 as the free-throw multiplier, since college hoops' rules about the team foul limit differ from those in the NBA. Offensive rebounds are subtracted because grabbing an offensive rebound simply extends the original possession, rather than creating a new possession. If offensive rebounds were not subtracted in this manner, opposing teams would not necessarily have the same number of possessions in a game.

Therefore, team ratings are simply calculated as:

and

Effective Field-Goal Percentage (eFG%) accounts for the fact that 3-pointers are worth an extra point, something ignored by traditional field-goal percentage. The formula is:

True Shooting Percentage takes this a step further by factoring in free throws. It is essentially points scored per shooting possession, but divided by two to look like field-goal percentage -- PTS/(2*(FGA + (.44*FTA)))

Rebound Rate is the estimated percentage of available rebounds a player or team grabs.

Player Efficiency Rating is John Hollinger's comprehensive linear-weights rating for a player's per-minute performance.

Pythagorean Record is what a team's expected record is based on points scored or allowed. This can be found by PF^14/(PF^14 + PA^14)

There are also several versions of passing ratings, a usage rating that measures how well a player does with the possession he uses, other general and skill specific defensive ratings and many other statistics and analytic ratios to aid understanding of player and team performance.

some APBRmetric type advanced stats

  • KnickerBlogger.Net Stats Page Another important hub for advanced statiscal data, it lists current player PER ratings, allows viewing of league leaders by specific advanced stats not always found at mainstream sport sites, team offense and defensive efficiency ratings and the 4 factor ratings breakouts
  • PopcornMachine.net, game flows (charts player movement in and out of the game aiding but not totally settling the question of who guarded whom). The game-by-game plus-minus data is an eagerly awaited addition to the standard boxscore.
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