Win Shares
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| Author |
Bill James and Jim Henzler |
|---|---|
| Subject | Baseball statistics |
| Publisher | STATS, Inc. |
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Publication date
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2002 |
| Pages | 729 |
| ISBN | |
| OCLC | 49718211 |
Win Shares is a book about baseball written by Bill James and Jim Henzler, published by STATS, Inc. in 2002. The book explains how to apply the concept of sabermetrics to assess the impact of player performance in a combination of several areas, including offensive, defensive, and pitching, to the overall performance of their team. The resulting "Win Share" also takes into account factors such as the era in which the player was active to allow easy comparisons between players from different eras. The book focuses primarily on the many formulae involved in computing the final number of win shares accumulated, as well as presenting lists of players ranked in various ways using the rating.
Win Shares Digital Update, a companion volume of tables and statistics through the 2001 season, was subsequently published in PDF form by STATS, Inc.
Win shares is the name of the metric developed by James in his book. It considers statistics for baseball players, in the context of their team and in a sabermetric way, and assigns a single number to each player for his contributions for the year. A win share represents one-third of a team win, by definition. If a team wins 80 games in a season, then its players will share 240 win shares. The formula for calculating win shares is complicated; it takes up pages 16–100 in the book. The general approach is to take the team's win shares (i.e., 3 times its number of wins), then divide them between offense and defense.
In baseball, all pitching, hitting and defensive contributions by the player are taken into account. Statistics are adjusted for park, league and era. On a team with equal offensive and defensive prowess, hitters receive 48% of the win shares and those win shares are allocated among the hitters based on runs created. An estimation is then made to decide what amount of the defensive credit goes to pitchers and what amount goes to fielders. Pitching contributions typically receive 35% (or 36%) of the win shares, defensive contributions receive 17% (or 16%) of the win shares. The pitching contributions are allocated among the pitchers based on runs prevented, the pitchers' analogue to runs created. Fielding contributions are allocated among the fielders based on a number of assumptions and a selection of traditional defensive statistics.
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