In
baseball statisticsStatistics play an important role in summarizing baseball performance and evaluating players in the sport.Dialog from the 1998 Kevin Costner motion picture For Love of the Game may epitomize the place of statistics in the minds of baseball players, reporters and fans:Jane Aubrey: Do you lose very...
,
earned run average (
ERA) is the
meanIn statistics, mean has two related meanings:* the arithmetic mean .* the expected value of a random variable, which is also called the population mean....
of
earned runIn 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...
s given up by a
pitcherIn 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 it or draw a walk. In the numbering system used to record defensive plays, the pitcher is...
per nine
innings 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...
. The ERA tells the average number of runs a pitcher would surrender over the course of a full game had he been kept in for the full nine innings. It is determined by dividing the number of earned runs allowed by the number of innings pitched and multiplying by nine. Runs resulting from batters who reach base on an error (even a pitcher error) and later score are called unearned runs, and do not count toward ERA.
Origins
Henry Chadwick is credited with first devising the statistic, which caught on as a measure of pitching effectiveness after
relief pitchingA relief pitcher or reliever is a baseball or softball pitcher who enters the game after the starting pitcher is removed due to injury, ineffectiveness, ejection from the game, or fatigue...
came into vogue in the 1900s. Prior to 1900 — and, in fact, for many years afterward — pitchers were routinely expected to pitch a
complete gameIn baseball, a complete game is the act of a pitcher pitching an entire game himself, without the benefit of a relief pitcher. A complete game can be either a win or a loss....
, and their
win-loss recordIn baseball, the win-loss record is the number of wins and losses a pitcher has accumulated either in his career or a single season....
was considered sufficient in determining their effectiveness.
Some means had to be found to calculate the apportionment of earned-run responsibility where multiple pitchers assume responsibility in a single game since pitchers have sole responsibility to earn strikes against opposing batters. A pitcher is assessed an
earned run for each earned run scored by a batter (or pinch-runner) who reached base while batting against that pitcher. After pitchers like
James Otis CrandallJames Otis Crandall was a right-handed pitcher and second baseman. He was the first player to be consistently used as a relief pitcher. Consequently, he was given the nickname Doc by Damon Runyon who said Crandall was "the physician of the pitching emergency". He played from 1908 to 1918,...
and Charlie Hall made names for themselves as relief specialists, gauging a pitcher's effectiveness became more difficult using the traditional method of tabulating wins and losses. The
National LeagueThe National League of Professional Baseball Clubs, known simply as the National League , is the older of two leagues constituting Major League Baseball, and the world's oldest extant professional team sports league...
first kept official earned run average statistics in
19121912 in sports describes the year's events in world sport.-American football:* College football national championship – Harvard Crimson and Penn State Nittany Lions -Association football:England...
(the statistic was called
Heydler's Statistic for a while, after then-NL secretary
John HeydlerJohn Arnold Heydler was an American executive in Major League Baseball.Born in La Fargeville, New York, he began working as a printer, eventually being employed at the U.S. Government Printing Office....
), with the
American LeagueThe American League of Professional Baseball Clubs, or simply the American League , is one of two leagues that make up Major League Baseball in the United States and Canada. It developed from the Western League, a minor league based in the Great Lakes states, that eventually aspired to major league...
following suit afterward.
Modern-day baseball encyclopedias notate ERAs for earlier years, but these were computed many years after the actual accomplishments.
Negro LeagueThe Negro leagues were American 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 1920 that...
pitchers are often rated by
RA, or total runs allowed, since the statistics available for Negro League games did not always distinguish between earned and unearned runs.
ERA in different decades and baseball eras
As with
batting averageBatting average is a statistic in both cricket and baseball measuring the performance of cricket batsmen and baseball hitters, respectively. The two statistics are related, in that baseball averages are directly descended from the concept of cricket averages....
, the definition of a "good" ERA varies from year to year. In the 1910s, a good ERA was below 2.00 (two earned runs allowed per nine innings). In the late 1920s and 1930s, when conditions of the game changed in a way that strongly favored hitters, a good ERA was below 4.00. Only high-caliber pitchers, for example
Dazzy VanceCharles Arthur "Dazzy" Vance was a star Major League Baseball starting pitcher during the 1920s.Born in Orient, Iowa, Vance played a decade in the minors before establishing himself as a big league player in 1922 with the Brooklyn Dodgers at the age of 31, when he went 18-12 with a 3.70 ERA and a...
or
Lefty GroveRobert Moses "Lefty" Grove was a pitcher in Major League Baseball.Born in Lonaconing, Maryland, Grove was a sandlot star in the Baltimore area during the 1910s...
, would consistently post an ERA under 3.00 during those years. In the 1960s, sub-2.00 ERAs returned, as other influences such as ballparks with different dimensions were introduced. Today, an ERA under 4.00 is again considered good, with pitchers such as
Greg MadduxGregory Alan "Greg" Maddux is a former Major League Baseball pitcher. He was the first pitcher in major league history to win the Cy Young Award for four consecutive years , a feat matched only by Randy Johnson...
and
Pedro MartínezPedro Jaime Martínez is a Major League Baseball starting pitcher for the Philadelphia Phillies. He is a three time Cy Young Award winner. At the time of his 200th win in April , Martínez had the highest winning percentage of any 200-game winner in modern baseball history...
achieving this mark.
The all-time single-season record for lowest ERA is 0.86, set by
Tim KeefeTimothy John "Tim" Keefe was an American pitcher in Major League Baseball. He was one of the most dominating pitchers of the 19th century and posted impressive statistics in one category or another for almost every season he pitched...
in
1880-American football:* College football national championship – Princeton Tigers and Yale Bulldogs * Walter Camp becomes a influential figure at the Massasoit House conventions where rules are debated and changed. His 1878 proposal to reduce the teams from fifteen players to eleven is passed in 1880,...
. The modern record is 0.96, set by
Dutch LeonardHubert Benjamin "Dutch" Leonard, was an American left-handed pitcher in Major League Baseball who had an 11-year career from 1913-1921, 1924-1925. He played for the Boston Red Sox and Detroit Tigers, and holds the major league record for the lowest single-season ERA of all time — 0.96 in 1914...
in
1914-American football:* College football national championship – Army Black Knights, Illinois Fighting Illini and Texas Longhorns -Association football:England...
. The lowest single-season ERA of a pitcher since 1950 is 1.12, achieved by
Bob GibsonPack Robert "Bob" Gibson is a former right-handed baseball pitcher, having played for the St. Louis Cardinals from to...
in 1968. The career record is 1.82, held by
Ed WalshEdward Augustine Walsh was a Major League Baseball pitcher. He holds the record for lowest career ERA, 1.82.Born in Plains Township, Pennsylvania, Walsh had a brief though remarkable major league career. He made his major league debut in with the Chicago White Sox and pitched his first full...
(1904-17). The active player with the lowest career ERA (among those with more than 1,000 innings pitched) is
Mariano RiveraMariano Rivera is a Panamanian professional baseball player who has spent his entire Major League Baseball career with the New York Yankees. Nicknamed "Mo", the right-handed Rivera has served as a relief pitcher for most of his career...
, with an ERA of 2.29 through the
20082008 in sports describes the year's events in world sport.-American football:* Louisiana State University Tigers defeat The Ohio State University Buckeyes 38-24 in the 2008 BCS National Championship Game, thus becoming the first two-time BCS National Champions, and the first BCS titlists with two...
season.
Some sources may list players with
undefined or infinite career ERAs. This can happen if a pitcher allows one or more earned runs without retiring a batter (usually in a single appearance). Additionally, an undefined ERA occasionally occurs at the beginning of a baseball season. It is sometimes incorrectly displayed as zero or as the lowest ranking ERA, even though it is more akin to the highest.
In modern baseball, ERAs can be interpreted in the following way:
| ERA |
Meaning |
| <2.00 |
Considered exceptional and is rare. |
| 2.00 to 3.00 |
Excellent, only achieved by best pitchers in the league. |
| 3.00 to 4.00 |
Better than average. |
| 4.00 to 5.00 |
Average. |
| 5.00 to 6.00 |
Worse than average. |
| >6.00 |
Consistently having an ERA this high risks demotion to the bullpen, or a lower league. |
ERA: starters vs. relievers; DH rule; ballpark; altitude & climate
It can be very misleading to judge
relief pitchers solely on ERA, because they are charged only for runs scored by batters who reached base while batting against them. Thus, if a relief pitcher enters the game with his team leading by 1 run, with 2 outs and the bases loaded, and then gives up a single which scores 2 runs, he is not charged with those runs. If he retires the next batter (and pitches no more innings), his ERA for that game will be 0.00 despite having surrendered the lead. (He is likely recorded with a blown save in this situation.)
Starting pitchers operate under the same rules but are almost never called upon to start pitching with runners already on base. In addition, relief pitchers know beforehand that they will only be pitching for a relatively short while, allowing them to throw each pitch with maximum energy, unlike starters who typically need to keep something in reserve in case they are asked to pitch 7 or more innings. This freedom to use their maximum energy for a few innings, or even for just a few batters, helps relievers keep their ERAs down.
ERA, taken by itself, can also be misleading when trying to objectively judge
starting pitcherIn baseball or softball, a starting pitcher is the pitcher who delivers the first pitch to the first batter of a game. A pitcher who enters the game after the first pitch of the game is a relief pitcher....
s, though not to the extent seen with relief pitchers. The advent of the
designated hitterIn baseball, the designated hitter rule is the common name for Major League Baseball Rule 6.10, an official position adopted by the American League in 1973 that allows teams to designate a player, known as the designated hitter , to bat in place of the pitcher each time he would otherwise come to...
rule in the American League in 1973 made the pitching environment significantly different. Since then, pitchers spending all or most of their careers in the AL have been at a disadvantage in maintaining low ERAs, compared to National League pitchers who can often get an easy out when pitching to the opposition's pitcher, who is usually not a very good batter. (Interestingly, though,
Pedro MartinezPedro Jaime Martínez is a Major League Baseball starting pitcher for the Philadelphia Phillies. He is a three time Cy Young Award winner. At the time of his 200th win in April , Martínez had the highest winning percentage of any 200-game winner in modern baseball history...
and
Mariano RiveraMariano Rivera is a Panamanian professional baseball player who has spent his entire Major League Baseball career with the New York Yankees. Nicknamed "Mo", the right-handed Rivera has served as a relief pitcher for most of his career...
, the ERA kings of the last decade or so, have been mostly active in the American League.) Since 1997, when teams began playing teams from the other league during the regular season, the DH rule is in effect only when such
interleague games are played in an American League park.
This difference between the leagues (the DH) also affects
relievers, but not to the same degree, as National League relievers actually pitch to pitchers far less than do NL starters for a number of reasons, chiefly because relievers are usually active in later innings when
pinch hitterIn baseball, a pinch hitter is a substitute batter. Batters can be substituted at any time while the ball is dead ; the manager may use any player that has not yet entered the game as a substitute...
s tend to be used in the pitcher's batting spot.
ERA is also affected somewhat by the
ballpark in which a pitcher's team plays half its games, as well as the tendency of hometown official scorers to assign errors instead of base hits in plays that could be either.
As an extreme example, pitchers for the
Colorado RockiesThe Colorado Rockies are a Major League Baseball team based in Denver, Colorado. Established in 1991, they started play in 1993, the Rockies play in the West Division of the National League. The team is named after the Rocky Mountains, which pass through Colorado, just west of Denver...
have historically faced many problems, all damaging to their ERAs. The combination of high
altitude (5,280 ft. or 1,609 m.)
and a semi-arid
climate in
DenverThe City and County of Denver is the capital and the most populous city of the state of Colorado, in the United States. Denver is a consolidated city-county located in the South Platte River Valley on the High Plains just east of the Front Range of the Rocky Mountains...
causes fly balls to travel up to 10% farther than at sea level. Denver's altitude and low humidity also reduce the ability of pitchers to throw effective breaking balls, due to both reduced air resistance and difficulty in gripping very dry baseballs. These conditions have been countered to some extent since 2002 by the team's use of
humidorA humidor is any kind of box or room with constant humidity – and often temperature as well – used to store cigars, cigarettes, or pipe tobacco. For private use, small wooden or acrylic glass humidor boxes for a few dozen cigars are used, while cigar shops may have walk-in humidors,...
s to store baseballs before games. These difficult circumstances for Rockies pitchers may not adversely affect their won-lost records, since opposing pitchers must deal with the same problems. Indeed, hometown hurlers have some advantage in any given game since they are physically acclimated to the altitude and often develop techniques to mitigate the challenges of this ballpark. Still, conditions there tend to inflate Rockie ERAs relative to the rest of the league.
Sabermetric treatment of ERA
In modern baseball,
sabermetricsSabermetrics is the analysis of baseball through objective evidence, especially baseball statistics. The term is derived from the acronym SABR, which stands for the Society for American Baseball Research...
uses several
defense independent pitching statisticsIn baseball, defense-independent pitching statistics measure a pitcher's effectiveness based only on plays that do not involve fielders: home runs allowed, strikeouts, hit batters, walks, and, more recently, fly ball percentage, ground ball percentage, and line drive percentage...
including a
Defense-Independent ERAIn baseball statistics,Defense-Independent ERA , created by Voros McCracken, projects what a pitcher's earned run average would have been, if not for the effects of defense and luck on the actual games in which he pitched.-Method:...
in an attempt to measure a pitcher's ability regardless of factors outside his control. Further, because of the dependence of ERA on factors over which a pitcher has little control, forecasting future ERAs on the basis of the past ERAs of a given pitcher is not very reliable and can be improved if analysts rely on other performance indicators such as strike out rates and walk rates. For example, this is the premise of
Nate SilverNathaniel Read Silver is an American statistician, journalist, and writer. After residing in Chicago, Illinois for thirteen years, he moved to New York City in 2009....
's forecasts of ERAs using his
PECOTAPECOTA, a backronym for Player Empirical Comparison and Optimization Test Algorithm, is a sabermetric system for forecasting Major League Baseball player performance. The acronym was actually based on the name of journeyman major league player Bill Pecota, who with a lifetime batting average of...
system. Silver also developed a "quick" earned run average (QuikERA or QERA) to calculate an ERA from peripheral statistics including strikeouts, walks, and groundball percentage. Unlike
peripheral ERAPeripheral ERA is a pitching statistic created by the Baseball Prospectus team. It is the expected earned run average taking into account park-adjusted hits, walks, strikeouts, and home runs allowed. Unlike Voros McCracken's DIPS, hits allowed are included...
OR PERA, it does not take into account park effects.
All-time career leaders
| Rank |
ERA |
Player |
Team(s) |
Year(s) |
| 1 |
1.82 |
Ed WalshEdward Augustine Walsh was a Major League Baseball pitcher. He holds the record for lowest career ERA, 1.82.Born in Plains Township, Pennsylvania, Walsh had a brief though remarkable major league career. He made his major league debut in with the Chicago White Sox and pitched his first full...
|
Chicago (AL)The Chicago White Sox are a Major League Baseball team based in Chicago, Illinois. The White Sox play in the American League's Central Division. Since , the White Sox have played in U.S. Cellular Field, which was originally called New Comiskey Park and nicknamed The Cell by local fans...
, Boston (NL)The Atlanta Braves are a professional baseball team based in Atlanta, Georgia. The Braves are a member of the Eastern Division of Major League Baseball's National League. From to the present, the Braves have played in Turner Field....
|
1904–17 |
| 2 |
1.89 |
Addie JossAdrian Joss was a Major League Baseball pitcher in the early 20th century.-Early life:He was born in the unincorporated community of Woodland in Dodge County, Wisconsin, where his father was a cheese maker. Several of his nicknames in baseball reflected this. As a youth, Joss was a star athlete at...
|
Cleveland (NL)The Cleveland Indians are a professional baseball team based in Cleveland, Ohio. They are in the Central Division of Major League Baseball's American League. Since , they have played in Progressive Field . The team's spring training facility is in Goodyear, Arizona...
|
1902–10 |
| 3 |
1.89 |
Jim Devlin James Alexander Devlin was an American Major League Baseball player who played mainly as a first baseman early in his career, then as a pitcher in the latter part...
|
Chicago (NA) White Stockings or "Chicago White Stockings" was an original name of two professional baseball clubs in Chicago, Illinois, namely the two Major League Baseball clubs that operate today* Chicago Cubs...
, Louisville (NL)The Louisville Grays were a 19th century U.S. baseball team and charter member of the National League, based in Louisville, Kentucky. They played two seasons, 1876 and 1877, and compiled a record of 65–61. Their home games were at the Louisville Baseball Park. The Grays were owned by...
|
1875-77 |
| 4 |
2.02 |
Jack PfiesterJohn Albert Pfiester , is a former professional baseball player who pitched in the Major Leagues from 1903-1911....
|
Pittsburgh (NL)The Pittsburgh Pirates are a Major League Baseball club based in Pittsburgh, Pennsylvania. They play in the Central Division of the National League, and are five-time World Series Champions, in addition to the distinction of playing in the first modern World Series. The Pirates are also often...
, Chicago (NL)The Chicago Cubs are an American professional baseball team based in Chicago, Illinois. They are members of the Central Division of Major League Baseball's National League. They are one of two Major League clubs based in Chicago , the Cubs are also one of the two remaining charter members of the...
|
1903-04, 1906-11 |
| 5 |
2.03 |
Smoky Joe Wood |
Boston (AL)The Boston Red Sox are a member of the Major League Baseball’s American League Eastern Division. Since , the Red Sox's home ballpark has been Fenway Park. The "Red Sox" name originates from the iconic uniform feature....
, Cleveland (AL)The Cleveland Indians are a professional baseball team based in Cleveland, Ohio. They are in the Central Division of Major League Baseball's American League. Since , they have played in Progressive Field . The team's spring training facility is in Goodyear, Arizona...
|
1908-15, 1917-22 |
See also
- 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...
(Park-adjusted ERA)
- Catcher's ERA
Catcher's ERA or CERA in baseball statistics is the earned run average of the pitchers pitching when the catcher in question is catching. Its primary purpose is to measure a catcher's game-calling, rather than his effect on the opposing team's running game. Craig Wright first described the...
- Component ERA
Component ERA or ERC is a baseball statistic invented by Bill James. It attempts to forecast a pitcher's earned run average from the number of hits and walks allowed rather than the standard formula of average number of earned runs per nine innings...
- Defense-Independent ERA
In baseball statistics,Defense-Independent ERA , created by Voros McCracken, projects what a pitcher's earned run average would have been, if not for the effects of defense and luck on the actual games in which he pitched.-Method:...
- 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...
- PERA
Peripheral ERA is a pitching statistic created by the Baseball Prospectus team. It is the expected earned run average taking into account park-adjusted hits, walks, strikeouts, and home runs allowed. Unlike Voros McCracken's DIPS, hits allowed are included...
- QERA
- Run average
In baseball statistics, run average refers to measures of the rate at which runs are allowed or scored. For pitchers, the run average is the number of runs—earned or unearned—allowed per nine innings...