In
sabermetrics
Sabermetrics, or originally SABRmetrics, is the empirical analysis of baseball, especially baseball statistics that measure in-game activity. Sabermetricians collect and summarize the relevant data from this in-game activity to answer specific ques ...
and
basketball analytics, similarity scores are a method of comparing
baseball
Baseball is a bat-and-ball sport played between two teams of nine players each, taking turns batting and fielding. The game occurs over the course of several plays, with each play generally beginning when a player on the fielding tea ...
and
basketball
Basketball is a team sport in which two teams, most commonly of five players each, opposing one another on a rectangular Basketball court, court, compete with the primary objective of #Shooting, shooting a basketball (ball), basketball (appr ...
players (usually in
MLB
Major League Baseball (MLB) is a professional baseball organization and the oldest major professional sports league in the world. MLB is composed of 30 total teams, divided equally between the National League (NL) and the American League (AL), ...
or the
NBA
The National Basketball Association (NBA) is a professional basketball league in North America. The league is composed of 30 teams (29 in the United States and 1 in Canada) and is one of the major professional sports leagues in the United St ...
) to other players, with the intent of discovering who the most similar historical players are to a certain player.
Similarity scores are among the many original sabermetric concepts first introduced by
Bill James
George William James (born October 5, 1949) is an American baseball writer, historian, and statistician whose work has been widely influential. Since 1977, James has written more than two dozen books devoted to baseball history and statistics. ...
. James initially created the concept as a way to effectively compare non-
Hall of Fame
A hall, wall, or walk of fame is a list of individuals, achievements, or other entities, usually chosen by a group of electors, to mark their excellence or Wiktionary:fame, fame in their field. In some cases, these halls of fame consist of actu ...
players to players in the Hall, to see who was either on track to make the HOF, or to determine if any eligible players had been snubbed by the selection committee. For example, if the most similar players to a non-HOFer were all in the Hall of Fame, one could effectively argue that that player should be in the Hall.
More recently, similarity scores have been used to determine career paths and projected statistics for players. The logic behind this line of thought is simple: players often follow similar career trajectories to their most similar players, so the historical similar players' performance in years after the active player's current age should be a good predictor of that active player's future production. An example of this would be the
Football Outsiders
Football Outsiders (FO) is a website started in July 2003 which focuses on advanced statistical analysis of the NFL. The site is run by a staff of regular writers, who produce a series of weekly columns using both the site's in-house statistics ...
' discovery that all but the highest caliber of
wide receivers suffer a marked decline after their seventh season in the
NFL, a fact that bore out for the receivers selected in the
1996 NFL Draft
The 1996 NFL draft was the procedure by which National Football League teams selected amateur college football players. It is officially known as the NFL Annual Player Selection Meeting. The draft was held April 20–21, 1996, at the Paramount ...
when their production collectively slipped.
Aaron Schatz
Football Outsiders (FO) is a website started in July 2003 which focuses on advanced statistical analysis of the NFL. The site is run by a staff of regular writers, who produce a series of weekly columns using both the site's in-house statistics ...
, "Hard Times for the Class of '96"
FootballOutsiders.com (July 8, 2004)
Many baseball analysts have augmented James' method over the years, or come up with their own system of measuring similarity. ''
Baseball Prospectus
Baseball Prospectus (BP) is an organization that publishes a website, BaseballProspectus.com, devoted to the sabermetric analysis of baseball. BP has a staff of regular columnists and provides advanced statistics as well as player and team perf ...
'' employs a projection system developed by
Nate Silver
Nathaniel Read Silver (born January 13, 1978) is an American statistician, writer, and poker player who analyzes baseball (see sabermetrics), basketball, and elections (see psephology). He is the founder and editor-in-chief of ''FiveThirtyEight' ...
known as
PECOTA PECOTA, an acronym for ''Player Empirical Comparison and Optimization Test Algorithm'', is a sabermetric system for forecasting Major League Baseball player performance. The word is a backronym based on the name of journeyman major league player Bil ...
which applies
nearest neighbor analysis to calculate similarities between players from different eras. ''Pro Football Prospectus'' (written by
Football Outsiders
Football Outsiders (FO) is a website started in July 2003 which focuses on advanced statistical analysis of the NFL. The site is run by a staff of regular writers, who produce a series of weekly columns using both the site's in-house statistics ...
) has their own system (dubbed "KUBIAK" after longtime
Broncos
A bucking horse is any breed or either gender of horse with a propensity to buck. They have been, and still are, referred to by various names, including bronco, broncho, and roughstock.
The harder they buck, the more desirable they are for rod ...
backup
quarterback
The quarterback (commonly abbreviated "QB"), colloquially known as the "signal caller", is a position in gridiron football. Quarterbacks are members of the offensive platoon and mostly line up directly behind the offensive line. In modern Ame ...
Gary Kubiak
Gary Wayne Kubiak (born August 15, 1961) is a former American football coach and quarterback. He served as head coach for the NFL's Houston Texans from 2006 Houston Texans season, 2006 to 2013 Houston Texans season, 2013 and the Denver Broncos f ...
) for projecting future performance.
John Hollinger
John Hollinger (born May 17, 1971) is the former Vice President of Basketball Operations for the Memphis Grizzlies of the National Basketball Association (NBA) and current Senior NBA columnist at The Athletic.
Prior to December 2012, he was an a ...
developed a similar system for basketball players in his ''Pro Basketball Forecast'' series of books, and several APBRmetricians have expanded on his methodology. Similarity scores are also used extensively in many statistical forecasting programs.
References
{{reflist
External links
Baseball Reference which employs a similarity method much like James' original method
Basketball-Reference.com which features a complex similarity-score system for NBA players
Football OutsidersBaseball Prospectus which uses similarity scores in
PECOTA PECOTA, an acronym for ''Player Empirical Comparison and Optimization Test Algorithm'', is a sabermetric system for forecasting Major League Baseball player performance. The word is a backronym based on the name of journeyman major league player Bil ...
that are calculated in a way that differs significantly from James' method.
Ken Pomeroy of Basketball Prospectuswho uses similarity scores for college basketball players.
Baseball statistics
Basketball statistics
American football terminology
Bill James