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In baseball statistics, slugging percentage (SLG) is a popular measure of the power of a hitter. It is calculated as total bases divided by at bats:
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where AB is the number of at-bats for a given player, and 1B, 2B, 3B, and HR are the number of singles, doubles, triples, and home runs, respectively. Walks are specifically excluded from this calculation. The name is a misnomer, as the statistic is not a percentage but a scale of measure whose computed value is a rational number in the interval [0, 4].
For example, in 1920, Babe Ruth played his first season for the New York Yankees. In 458 at bats, Ruth had 172 hits, comprising 73 singles, 36 doubles, 9 triples, and 54 home runs, which brings the total base count to (73 × 1) + (36 × 2) + (9 × 3) + (54 × 4) = 388. His total number of bases (388) divided by his total at-bats (458) is .847, his slugging percentage for the season, setting a record that stood until 2001, when Barry Bonds achieved 411 bases in 476 at-bats, bringing his slugging percentage to .863, unmatched since.
Significance
Long after it was first invented, slugging percentage gained new significance when baseball analysts realized that it combined with on-base percentage (OBP) to form a very good measure of a player's overall offensive production (in fact, OBP + SLG was originally referred to as "production" by baseball writer and statistician Bill James). A predecessor metric was developed by Branch Rickey in 1954. Rickey, in Life magazine, suggested that combining OBP with what he called "extra base power" (EBP) would give a better indicator of player performance than typical Triple Crown stats. EBP was a predecessor to slugging percentage.
Allen Barra and George Ignatin were early adopters in combining the two modern-day statistics, multiplying them together to form what is now known as "SLOB" (Slugging × On-Base). Bill James applied this principle to his runs created formula several years later (and perhaps independently), essentially multiplying SLOB × At-Bats to create the formula:
In 1984, Pete Palmer and John Thorn developed perhaps the most widespread means of combining slugging and on-base percentage: OPS. "OPS" simply stands for "on-base plus slugging", and is a simple addition of the two values. Because it is easy to calculate, OPS has been used with increased frequency in recent years as a shorthand form to evaluate contributions as a batter.
Perfect slugging percentage
The maximum numerically possible slugging percentage is 4.000. A number of MLB players (117 through the end of the 2016 season) have momentarily had a 4.000 career slugging percentage by homering in their first major league at-bat.
No player has ever retired with a 4.000 slugging percentage, but four players tripled in their only MLB at-bat and therefore share the record of a career slugging percentage of 3.000 (when evaluated without regard to a minimum number of games played or plate appearances). The players are Eric Cammack (2000 Mets), Scott Munninghoff (1980 Phillies), Eduardo Rodríguez (1973 Brewers), and Charlie Lindstrom (1958 White Sox).