APBRmetrics
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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.
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 (Offensive Rating) and points allowed per 100 possessions (Defensive Rating).
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."
A fuller explanation of possession based analysis is available in "A Starting Point for Analyzing Basketball Statistics" in the Journal of Quantitative Analysis in Sports. {http://www.bepress.com/jqas/vol3/iss3/1}
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[edit] 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. Among these people were Dave Heeren, Bob Bellotti, and Martin Manley.
Beginning in the 1990s, Dean Oliver popularized the use of possession statistics. Oliver and John Hollinger are credited with moving this use of basketball statistics into the view of more basketball fans through their websites in the late 1990s. 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 fine-tuning the methods and their usage and advancing new approaches to research questions through the active APBRmetrics forum.
In the wake of the best-selling book Moneyball, which glamorized Sabermetrics, APBRmetric approaches began to receive some attention from the media and NBA teams.{see list of media articles near bottom of this page http://www.sonicscentral.com/statsite.html} The goal was to find a more objective method of analyzing player performance and 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 Web site 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 for basketball (it was a common measurement in ice hockey). 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 written play by play records but aren't perfect either.)
During the 2006 NBA Playoffs, Synergy Sports Technology provided a free trial of a site that combined video of every NBA game with statistical breakdowns of player tendencies similar to those long in use amongst NBA teams -- going left vs right, being the ball handler on the pick and roll, etc. This combination of video and statistics is currently being used by a number of NBA teams. Public access has been discontinued indefinitely.
[edit] Prominent APBRmetricians
Roland Beech is the proprietor of 82games.com and has contributed his analysis to ESPN.com and SI.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). 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 computer simulation for NBA basketball called B-BALL. Chaikin's simulation can simulate hundreds, even thousands of games in minutes to assess the impact of various lineup and rotation changes or the value of a player signed via trade or free agency. It has been used by several NBA teams.[citation needed] He offers it and a comprehensive historical sports statistics database for pro baseball, basketball, football, and hockey (a free download) at his website www.bballsports.com.
David Berri is a professor of economics at Cal State-Bakersfield who teamed with peers Martin Schmidt and Stacey Brook to write Wages of Wins. Published in 2006, the book brought the work of sports economists to a wider group of readers and focused largely on the NBA.
Kevin Broom has been a columnist at RealGM.com and other basketball related websites. Broom's work includes creation of the Salary Formula, which translates individual statistics to NBA cap dollars; as well as the Diamond Rating, which can help identify players underrated by their per game stats. Broom is also a leader in evaluating defense through collecting and analyzing new statistics not captured in box scores.
Mike Goodman is the creator of the EWins method for evaluating the importance of player contributions to team winning. It makes use of its own custom weights & unique adjustments and presents player value in terms of wins added (per season or playoff series).
Dave Heeren wrote a series of Basketball Abstract books in the early 1990s and invented the most prominent early rating system, TENDEX.
John Hollinger authored four books in the Pro Basketball Forecast/Prospectus series and is 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 the system to regular NBA fans.
Justin Kubatko developed and administers Basketball-Reference.com, a site that provides much relied upon and easy access to regular and many of the advanced basketball statistics, much of the data not available anywhere else on the net for before the most recent seasons. He also adapted an idea from Bill James called WinShares to basketball to estimate player contribution to a team's level of winning based on individual offensive performance and team defense while the player is on the court. ESPN.com has called the site "[T]he world's best hoops history site."
Ed Kupfer A self-taught statistical wizard, Kupfer has made numerous notable high technique and graphical contributions at the APBRmetrics board and is reportedly a consultant for the Houston Rockets, working alongside Sam Hinkie and GM Daryl Morey.
Mike Kurylo is the creator of KnickerBlogger.Net and the former CourtsideTimes.Net. KnickerBlogger.Net doubles as an APBRmetric-friendly NBA blog and stat page. The stat page is updated daily with advanced statistics for teams and individuals for the current NBA season.
Dean Oliver is a former player, coach, and scout, now serving in the front office of the Denver Nuggets. His longtime website, Journal of Basketball Studies, and subsequent 2003 book, Basketball on Paper, brought him recognition as a principal leader in the field. 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 development of the Four Factors of Basketball Success (field-goal shooting, offensive rebounds, turnovers and getting to the free-throw line) also helps provide a useful framework for evaluation of players and teams.
Kevin "Al" Pelton is a sportswriter who covers the Seattle SuperSonics and Seattle Storm for their respective Web sites. Pelton is a columnist for BasketballProspectus.com and has written for 82games.com, Hoopsworld.com and SI.com. He has worked to acquaint mainstream basketball fans with statistical analysis. He moderates the APBRmetrics forum.
Dan Rosenbaum is a consultant for the Cleveland Cavaliers. Rosenbaum's work has focused on adjusted plus-minus ratings, which takes into account the quality of the players playing with and against a player and adjusts his plus-minus accordingly.
Jeff Sagarin and Wayne Winston pioneered adjusted plus-minus statistics with their WINVAL system, which has been used extensively by the Dallas Mavericks.
[edit] Common statistics
Among the growing list of APBRmetric 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:
- Possessions = .96 * (FGA − ORb + TO + (.44 * FTA))
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 the NCAA's 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.
The .96 multiplier adjusts for team rebounds. Because these are not considered offensive rebounds, the formula slightly overestimates the number of possessions per team without the multiplier.
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 linear-weights rating for a player's per-minute performance which reduces a player's total performance into a single number.
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.
[edit] External links
- APBRmetrics Message Board The central discussion source for APBRmetrics
- 82games.com A wealth of player and team data, +/-, counterpart, by position, time on clock. Also conducts in-depth studies of specialized questions often asked before but not rigorously analyzed.
- AlleyOop.com, Hollinger's Web site (mainly good for links to articles, book buying and archives)
- apbr.org Home of the Association for Professional Basketball Research.
- APBRmetrics Central Another list of resources
- BasketballProspectus.com A new online basketball analysis site from the publishers of the Baseball Prospectus.
- Basketball-Reference.com, historical stats with an APBRmetrics influence
- BasketballValue.com, raw plus-minus and lineup data
- BellottiBasketball.com, statistical consulting service for professional basketball teams
- BBALLsports.com, Bob Chaikin's site for computer basketball simulation and historical sports statistics database
- CountTheBasket.com the most comprehensive index of available stats by type and date on various sites around the web.
- DougStats.com, raw statistical data that can be copied into Excel for manipulation.
- Hollinger's ESPN Insider Archive
- HoopsAnalyst.com, research columns and a strong set of information regarding trades
- Hoopsstats .com A wide range of player and team statistics and many often unique splits.
- Journal of Basketball Statistics, Oliver's Web site (primarily useful to understand definitions if you do not have his newer book and to archive his early work)
- Ken Pomeroy's site, which tracks stats for College Basketball including advanced NCAA stats
- KnickerBlogger.Net Stats Page Another important hub for advanced statistical 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 Four Factor ratings
- PopcornMachine.net, game flows (charts player movement in and out of the game aiding but not totally settling the question of who guarded whom).
- "Rocket Science", Houston Press article on Daryl Morey using statistical analysis to manage the Houston Rockets.
- [1], "Using Box Scores to Analyze a Position's Value to WInning Games." A recent academic research paper looking at impact of player contributions by position and by statistical category.
- APBRmetrics.com, Sports picks based on APBRmetrics
