Earned Run Average

Earned Run Average (ERA) is a statistic in baseball that shows the average number of opposing runs (points) a pitcher allows in nine innings . The calculation does not include all runs that this pitcher has submitted, only the so-called earned runs. According to the scoring rules, only those runs are counted as earned runs that are scored without the help of Errors and Passed Balls. This is to subtract the performance of the defense, so that the earned run average only measures the quality of the pitching. The earned run average indicates how many points an opposing team would score against this pitcher if he were to pitch a full game (without extra innings) and his team did not make any mistakes on the defensive.

The official scorer decides whether a run is an earned run by reconstructing the course of the game without errors or passed balls. All runs scored in this fictional game are earned runs. Determining the earned runs is one of the most difficult tasks of the scorer due to the complex rules.

Although the performance of the defensive cannot be fully calculated, the earned run average is still considered a meaningful statistic and the most important statistic in pitching.

The ERA is calculated using the formula:

{\ displaystyle {ERA} = 9 \ cdot {\ frac {\ mathrm {Earned ~ Runs ~ Allowed}} {\ mathrm {Innings ~ Pitched}}}}

With:

Earned Runs Allowed = earned runs made by the pitcher.
Innings Pitched = the number of innings a pitcher has played during the season.

Eternal leaderboard

rank	ERA	player	Team (s)	Year (s)
1	1.82	Ed Walsh	Chicago (AL) , Boston (NL)	1904-1917
2	1.89	Addie Joss	Cleveland (NL)	1902-1910
3	1.89	Jim Devlin	Chicago (NA) , Louisville (NL)	1875-1877
4th	2.02	Jack Pfiester	Pittsburgh (NL) , Chicago (NL)	1903-1904, 1906-1911
5	2.03	Smoky Joe Wood	Boston (AL) , Cleveland (AL)	1908-1915, 1917-1922

Individual evidence

↑ Christian Posny, Sven Müncheberg: Rules Booklet Baseball - Revised 2007. German Baseball and Softball Association e. V. (ed.). 6. revised Edition. Meyer & Meyer Verlag, Aachen 2008, ISBN 978-3-89899-365-4 .

[1] Christian Posny, Sven Müncheberg: Rules Booklet Baseball - Revised 2007. German Baseball and Softball Association e. V. (ed.). 6. revised Edition. Meyer & Meyer Verlag, Aachen 2008, ISBN 978-3-89899-365-4 .