Title: Earned run average
Content:   In baseball statistics, earned run average (ERA) is the average of earned runs allowed by a pitcher per nine innings pitched (i.e. the traditional length of a game). It is determined by dividing the number of earned runs allowed by the number of innings pitched and multiplying by nine. Thus, a lower ERA is better. Runs resulting from passed balls or defensive errors (including pitchers' defensive errors) are recorded as unearned runs and omitted from ERA calculations.
Title: Glossary of baseball (E)
Content: 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. Runs resulting from defensive errors are recorded as unearned runs and omitted from ERA calculations. 
Title: Glossary of baseball (E)
Content: See earned run average. 
Title: Earned run
Content:  In baseball, an earned run is any run that was fully enabled by the offensive team's production in the face of competent play from the defensive team. Conversely, an unearned run is a run that would not have been scored without the aid of an error or a passed ball committed by the defense. An unearned run counts just as much as any other run for the purpose of determining the score of the game. However, it is "unearned" in that it was, in a sense, "given away" by the defensive team. Both total runs and earned runs are tabulated as part of a pitcher's statistics. However, earned runs are specially denoted because of their use in calculating a pitcher's earned run average (ERA), the number of earned runs allowed by the pitcher per nine innings pitched (i.e., averaged over a regulation game). Thus, in effect, the pitcher is held personally accountable for earned runs, while the responsibility for unearned runs is shared with the rest of the team. To determine whether a run is earned, the official scorer must reconstruct the inning as it would have occurred without errors or passed balls.
Title: Earned run average
Content:  batter they do not retire at the plate moves to base, and eventually reaches home, scoring a run. A pitcher is assessed an earned run for each run scored by a batter (or that batter's pinch-runner) who reaches base while batting against that pitcher. The National League first tabulated official earned run average statistics in 1912 (the outcome was called "Heydler's statistic" for a while, after then-NL secretary John Heydler), and the American League later accepted this standard and began compiling ERA statistics. Baseball encyclopedias will often display ERAs for earlier years, but these were computed retroactively. Negro league 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.
Title: Earned run average
Content:  In baseball statistics, runs per nine innings (denoted by R/9) is a measure of a pitcher's effectiveness in preventing runs; calculated as: (9 × runs allowed) / (innings pitched). In this way, it is different from the ERA in that all runs, rather than only earned runs, are included.
Title: Glossary of baseball (E)
Content: Any run for which the pitcher is held accountable (i.e., the run did not score as a result of a fielding error or a passed ball). Primarily used to calculate the earned run average. In determining earned runs, an error charged to a pitcher is treated exactly like an error charged to any other fielder. Some pitchers, notably Ed Lynch, referred to earned runs as "earnies". 
Title: Run average
Content: R = Runs ; IP = Innings pitched In baseball statistics, run average (RA) 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. 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.
Title: Earned run average
Content:  Henry Chadwick is credited with devising the statistic, which caught on as a measure of pitching effectiveness after relief pitching came into vogue in the 1900s. Prior to 1900&mdash;and, in fact, for many years afterward&mdash;pitchers were routinely expected to pitch a complete game, and their win-loss record was considered sufficient in determining their effectiveness. After pitchers like James Otis Crandall and Charley 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. Some criterion was needed to capture the apportionment of earned-run responsibility for a pitcher in games that saw contributions from other pitchers for the same team. Since pitchers have primary responsibility for putting opposing batters out, they must assume responsibility when 
Title: List of Major League Baseball annual ERA leaders
Content:  In baseball, earned run average (ERA) is a statistic used to evaluate pitchers, calculated as the mean of earned runs given up by a pitcher per nine innings pitched. A pitcher is assessed an earned run for each run scored by a baserunner who reached base while batting against that pitcher, whether by hit, base on balls or "walk", or being hit by a pitched ball; an earned run can be charged after the pitcher is relieved if he allows the runner before leaving the game. Runs scored by players who reach base on errors, passed balls, or catcher interference under special circumstances are treated as unearned runs, and do not count 

Question: What sport does earned run average play?
Answer: baseball.
America's pastime.
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