Earned Run (ER)
From SABR Encyclopedia
In baseball statistics, Earned Run (ER) is a count of how many runs a pitcher would have allowed with errorless play by his defense. Earned Runs are an official MLB statistic covered by rule 10.16 of the 2009 Official Rules[1]. Every inning during which an error or passed ball is committed by the defense that is followed by one or more runs scoring is reviewed by the Official Scorer. The Official Scorer reconstructs the inning without the passed balls and errors. At the end of the game, the Official Scorer adds the runs from the reconstructed innings to runs from clean innings (innings without errors and passed balls) and reports the sum as team earned runs. If only one pitcher pitched in a reconstructed inning, he has the same earned runs as the team for that inning. If two or more pitchers pitch in a reconstructed inning, pitchers do not get the benefit of errors and passed balls in the inning prior to their entrance per rule 10.16(i) of the 2009 Official Rules[2].
For instance, Cole Hamels starts the inning with a man reaching base on an error, then a walk, a pop up, and then Brad Lidge enters the game. Lidge gets the second out of the inning on a strikeout, then walks a batter and allows a homerun before retiring the last batter. The Phillies allowed four runs, two charged to Hamels and two to Lidge. Reconstructing this inning, all runs are unearned to the Phillies because Lidges strikeout would have been the third out and no runs had scored yet. Similarly, Hamels two runs were both unearned. But for Lidge, the Official Scorer reconstructs the inning from the point Lidge entered. The OS considers Lidge to enter with one out and give up Lidge's two runs before the third out. So both Lidges runs are earned. This is why a team's pitchers' earned runs can sum to more than the team's total.
[edit] History
Until 10.16(i) was added in 1969, team earned runs were divided among the pitchers [3]. If our example above had happened in 1968, Lidge would have had two unearned runs and no earned runs. Thus reliever ERAs after 1968 are at a disadvantage compared to ERAs prior to 1969.
The earned run statistic was added to the rule book in 1912 [3] and been slightly modified since. Researchers have figured out earned runs for pitchers prior to 1912 which now appear in current data bases.
After 1968, the better published sources of season statistics have a footnote explaing why team ERs are less than the sum of the teams pitchers ERs. Before rule 10 was restated a few years ago (circa 2006), the subsection was 10.18(i) and that rule subsection appears often in such footnotes.
Footnotes
- ↑ http://mlb.mlb.com/mlb/downloads/y2008/official_rules/10_the_official_scorer.pdf, retrieved on 2009-10-24.
- ↑ http://mlb.mlb.com/mlb/downloads/y2008/official_rules/10_the_official_scorer.pdf, retrieved on 2009-10-24.
- ↑ 3.0 3.1 The Baseball Encyclopedia 9th edition. New York: Macmillan, 1993.))
