Run average
Encyclopedia
In baseball statistics
, run average (RA) refers to measures of the rate at which run
s are allowed or scored. For pitcher
s, the run average is the number of runs—earned or unearned—allowed per nine innings. It is calculated using this formula:
where
Run average for pitchers differs from the more commonly used earned run average
(ERA) by adding unearned runs
to the numerator. This measure is also known as total run average (TRA) or runs allowed average. For batters, the run average is the number of runs scored per at bat.
, data on earned runs may be unavailable and RA may be the only statistic available. The analytical case for RA appeared as early as 1976, when sportswriter
Leonard Koppett
proposed that RA would be a better measure of pitcher performance than ERA. Subsequently, sabermetrician
Bill James
wrote, "I think that the distinction between earned runs and unearned runs is silly and artificial, a distinction having no meaning except in the eyes of some guy up in the press box."
In baseball, defense—that is, preventing the opponent from scoring runs—is the joint responsibility of the pitcher and the fielders
. ERA attempts to adjust for some of the influence of the fielders on a pitcher's runs allowed by removing runs that are scored because of fielding error
s—that is, unearned runs. However, removing unearned runs doesn't adequately adjust for the effects of defensive support, because it makes no adjustment for other important aspects of fielding, such as proficiency at turning double play
s, throwing out base stealers
, and fielding range
. Errors are the only aspect of fielding that ERA adjusts for, and are generally regarded as a small part of fielding in modern baseball.
Another problem with ERA is the inconsistency with which official scorer
s call plays as errors. The rules give scorers considerable discretion regarding the plays that can be called as errors. Researcher Craig R. Wright
found large differences between teams in the rate at which their scorers called errors, and even found some evidence of home team bias
—that is, calling errors to favor the statistics of players for the home team.
While ERA doesn't charge the pitcher for the runs that result from errors, it may tend to over correct for the influence of fielding. Even though unearned runs would not have scored without an error, in most cases the pitcher also contributes to the scoring of the unearned run—either by allowing the opposing player to reach base via a walk
or hit
, or by allowing a subsequent batter a hit that advances and scores the runner. During the early days of baseball history, this over correction for fielding errors caused pitchers on bad teams to be overrated in terms of ERA.
Removing unearned runs in calculating ERA may be useful if they are unrelated to pitcher performance, but Wright concludes that fielding errors are somewhat dependent on a pitcher's style. Because errors occur most often on ground balls, pitchers with high strikeout
rates who give up fly balls are likely to give up fewer unearned runs than groundball control-type pitchers
. For example, Ron Guidry
—a flyball power pitcher
—and Tommy John
—a groundball control pitcher—were teammates on the Yankees
from 1979 to 1982, supported by the same defense. During that period, 13.7% of John's runs allowed were unearned, compared to 9.8% of Guidry's. Wright concludes that this difference is attributable to their pitching styles, and thus, that unearned runs are partially attributable to the pitcher.
, it is possible to adjust RA for the ballpark effects
and compare it to the league average. The formula for this adjustment is:
where
Values of RA+ above 100 indicate better-than-average pitching performance. Unlike unadjusted RA, which must be higher than unadjusted ERA, a pitcher's adjusted RA+ can be either higher or lower than his adjusted ERA+.
Baseball statistics
Statistics play an important role in summarizing baseball performance and evaluating players in the sport.Since the flow of a baseball game has natural breaks to it, and normally players act individually rather than performing in clusters, the sport lends itself to easy record-keeping and statistics...
, run average (RA) refers to measures of the rate at which run
Run (baseball)
In baseball, a run is scored when a player advances around first, second and third base and returns safely to home plate, touching the bases in that order, before three outs are recorded and all obligations to reach base safely on batted balls are met or assured...
s are allowed or scored. For pitcher
Pitcher
In baseball, the pitcher is the player who throwsthe baseball from the pitcher's mound toward the catcher to begin each play, with the goal of retiring a batter, who attempts to either make contact with the pitched ball or draw a walk. In the numbering system used to record defensive plays, the...
s, the run average is the number of runs—earned or unearned—allowed per nine innings. It is calculated using this formula:
where
- R = RunsRun (baseball)In baseball, a run is scored when a player advances around first, second and third base and returns safely to home plate, touching the bases in that order, before three outs are recorded and all obligations to reach base safely on batted balls are met or assured...
- IP = Innings pitchedInnings pitchedIn baseball, innings pitched are the number of innings a pitcher has completed, measured by the number of batters and baserunners that are put out while the pitcher on the pitching mound in a game. Three outs made is equal to one inning pitched. One out counts as one-third of an inning, and two...
Run average for pitchers differs from the more commonly used earned run average
Earned run average
In baseball statistics, earned run average is the mean of earned runs given up by a pitcher per nine innings pitched. It is determined by dividing the number of earned runs allowed by the number of innings pitched and multiplying by nine...
(ERA) by adding unearned runs
Earned run
In baseball, an earned run is any run for which the pitcher is held accountable . Any runner who tags his base and reaches home plate is scored against the pitcher as an earned run...
to the numerator. This measure is also known as total run average (TRA) or runs allowed average. For batters, the run average is the number of runs scored per at bat.
Run average for pitchers
Although presentations of pitching statistics generally feature the ERA rather than the RA, the latter statistic is notable for both historical and analytical reasons. For early leagues or leagues for which statistics must be calculated from box scores, such as the Negro leaguesNegro league baseball
The Negro leagues were United States professional baseball leagues comprising teams predominantly made up of African Americans. The term may be used broadly to include professional black teams outside the leagues and it may be used narrowly for the seven relatively successful leagues beginning in...
, data on earned runs may be unavailable and RA may be the only statistic available. The analytical case for RA appeared as early as 1976, when sportswriter
Sports journalism
Sports journalism is a form of journalism that reports on sports topics and events.While the sports department within some newspapers has been mockingly called the toy department, because sports journalists do not concern themselves with the 'serious' topics covered by the news desk, sports...
Leonard Koppett
Leonard Koppett
Leonard Koppett was one of the most influential sportswriters of the 20th century.Born in Moscow, Koppett moved with his family from Russia to the United States when he was five years old...
proposed that RA would be a better measure of pitcher performance than ERA. Subsequently, sabermetrician
Sabermetrics
Sabermetrics is the specialized analysis of baseball through objective, empirical evidence, specifically baseball statistics that measure in-game activity. The term is derived from the acronym SABR, which stands for the Society for American Baseball Research...
Bill James
Bill James
George William “Bill” James is a 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...
wrote, "I think that the distinction between earned runs and unearned runs is silly and artificial, a distinction having no meaning except in the eyes of some guy up in the press box."
In baseball, defense—that is, preventing the opponent from scoring runs—is the joint responsibility of the pitcher and the fielders
Baseball positions
There are 9 fielding positions in baseball. Each position conventionally has an associated number which is used to score putouts...
. ERA attempts to adjust for some of the influence of the fielders on a pitcher's runs allowed by removing runs that are scored because of fielding error
Error (baseball)
In baseball statistics, an error is the act, in the judgment of the official scorer, of a fielder misplaying a ball in a manner that allows a batter or baserunner to reach one or more additional bases, when such an advance would have been prevented given ordinary effort by the fielder.The term ...
s—that is, unearned runs. However, removing unearned runs doesn't adequately adjust for the effects of defensive support, because it makes no adjustment for other important aspects of fielding, such as proficiency at turning double play
Double play
In baseball, a double play for a team or a fielder is the act of making two outs during the same continuous playing action. In baseball slang, making a double play is referred to as "turning two"....
s, throwing out base stealers
Stolen base
In baseball, a stolen base occurs when a baserunner successfully advances to the next base while the pitcher is delivering the ball to home plate...
, and fielding range
Range Factor
Range Factor is a baseball statistic developed by Bill James. It is calculated by dividing putouts and assists by number of innings or games played at a given defense position...
. Errors are the only aspect of fielding that ERA adjusts for, and are generally regarded as a small part of fielding in modern baseball.
Another problem with ERA is the inconsistency with which official scorer
Official scorer
In the game of baseball, the official scorer is a person appointed by the league to record the events on the field, and to send the official scoring record of the game back to the league offices...
s call plays as errors. The rules give scorers considerable discretion regarding the plays that can be called as errors. Researcher Craig R. Wright
Craig R. Wright
Craig R. Wright is a major proponent of sabermetrics, a baseball writer and historian.He was a very early pioneer in integrating science into major league baseball and first began working under that premise for the Texas Rangers, after the strike of 1981...
found large differences between teams in the rate at which their scorers called errors, and even found some evidence of home team bias
Bias
Bias is an inclination to present or hold a partial perspective at the expense of alternatives. Bias can come in many forms.-In judgement and decision making:...
—that is, calling errors to favor the statistics of players for the home team.
While ERA doesn't charge the pitcher for the runs that result from errors, it may tend to over correct for the influence of fielding. Even though unearned runs would not have scored without an error, in most cases the pitcher also contributes to the scoring of the unearned run—either by allowing the opposing player to reach base via a walk
Base on balls
A base on balls is credited to a batter and against a pitcher in baseball statistics when a batter receives four pitches that the umpire calls balls. It is better known as a walk. The base on balls is defined in Section 2.00 of baseball's Official Rules, and further detail is given in 6.08...
or hit
Hit (baseball)
In baseball statistics, a hit , also called a base hit, is credited to a batter when the batter safely reaches first base after hitting the ball into fair territory, without the benefit of an error or a fielder's choice....
, or by allowing a subsequent batter a hit that advances and scores the runner. During the early days of baseball history, this over correction for fielding errors caused pitchers on bad teams to be overrated in terms of ERA.
Removing unearned runs in calculating ERA may be useful if they are unrelated to pitcher performance, but Wright concludes that fielding errors are somewhat dependent on a pitcher's style. Because errors occur most often on ground balls, pitchers with high strikeout
Strikeout
In baseball or softball, a strikeout or strike-out occurs when a batter receives three strikes during his time at bat. A strikeout is a statistic recorded for both pitchers and batters....
rates who give up fly balls are likely to give up fewer unearned runs than groundball control-type pitchers
Control pitcher
A control pitcher is a pitcher who succeeds mostly by using accurate pitches, as opposed to a power pitcher who relies on velocity. By issuing a below average number of bases on balls he exhibits good control of his pitches...
. For example, Ron Guidry
Ron Guidry
Ronald Ames Guidry , nicknamed "Louisiana Lightning" and "Gator", is a former Major League Baseball left-handed pitcher. He played his entire 14-year baseball career for the New York Yankees...
—a flyball power pitcher
Power pitcher
In baseball, a power pitcher is a pitcher who relies on the velocity of his pitches, sometimes at the expense of accuracy. Power pitchers usually record a high number of strikeouts and statistics such as strikeouts per 9 innings pitched are common measures of power...
—and Tommy John
Tommy John
Thomas Edward John Jr. is a former left-handed pitcher in Major League Baseball whose 288 career victories rank as the seventh highest total among left-handers in major league history...
—a groundball control pitcher—were teammates on the Yankees
New York Yankees
The New York Yankees are a professional baseball team based in the The Bronx, New York. They compete in Major League Baseball in the American League's East Division...
from 1979 to 1982, supported by the same defense. During that period, 13.7% of John's runs allowed were unearned, compared to 9.8% of Guidry's. Wright concludes that this difference is attributable to their pitching styles, and thus, that unearned runs are partially attributable to the pitcher.
Adjusted RA+
Similar to adjusted ERA+Adjusted ERA+
Adjusted ERA+, often simply abbreviated to ERA+ or ERA plus, is a pitching statistic in baseball. It adjusts a pitcher's earned run average according to the pitcher's ballpark and the ERA of the pitcher's league...
, it is possible to adjust RA for the ballpark effects
Batting Park Factor
Batting Park Factor, also simply called Park Factor or BPF, is a baseball statistic that indicates the difference between runs scored in a team's home and road games. Most commonly used as a metric in the sabermetric community, it has found more general usage in recent years...
and compare it to the league average. The formula for this adjustment is:
where
- lgRA = park-adjusted league run average
- RA = the pitcher's run average.
Values of RA+ above 100 indicate better-than-average pitching performance. Unlike unadjusted RA, which must be higher than unadjusted ERA, a pitcher's adjusted RA+ can be either higher or lower than his adjusted ERA+.