Earned run average
Earned Run Average (ERA) is a statistic in baseball that indicates how many opposing runs (points) a pitcher allows on average in nine innings. However, the calculation does not include all the runs that this pitcher has given up, but only the so-called earned runs. According to the scoring rules, only the runs scored without the help of errors and passed balls are counted as earned runs. This is to factor out the performance of the defense, so the Earned Run Average only measures the quality of the pitching. So the Earned Run Average is how many points an opposing team would score against that pitcher if he pitched a full game (without extra innings) and his team made no errors defensively.
The Official Scorer decides whether a Run is an Earned Run by reconstructing the course of the game without Errors and Passed Balls. All runs scored in this fictional game are Earned Runs. Determining Earned Runs is one of the scorer's most difficult tasks due to the complex rules involved.
Although defensive performance can't be completely factored out, Earned Run Average is still considered a meaningful statistic and the most important statistic in pitching.
The ERA is calculated using the formula:
with:
Eternal leaderboard
Rank | ERA | Players | 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 |
4 | 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 |