Error
A judgment call by one person in the press box that changes a pitcher's ERA and a fielder's reputation.
What it actually is. An error is charged when the official scorer judges that a fielder's misplay allowed a batter to reach or a runner to advance when ordinary effort would have prevented it. Runs that score because of an error are unearned and do not count against the pitcher's earned run average. It is a subjective ruling, made by one person, and it is the only major statistic in baseball that works that way.
What somebody who knows the game gets out of it. The error is a nineteenth century idea and it measures the wrong thing, which is why modern defensive metrics ignore it entirely. It punishes a fielder for reaching a ball he should not have got to and rewards one who never moved, since a ball nobody touched cannot be an error. Outs Above Average and Defensive Runs Saved exist because the question worth asking is how many balls a fielder converted compared with what the average man at his position converts on the same batted ball, and errors cannot see that at all.
The numbers worth knowing. Errors per team per game have fallen from over three in the 1880s to around 0.55 now, which is mostly gloves and groundskeeping rather than skill. A shortstop making fifteen errors in a season is normal; the number tells you very little about whether he is any good.
What people get wrong about it. An unearned run is not a run that did not happen. A pitcher who gives up four runs of which three are unearned still lost the game by four. ERA was built to separate a pitcher from his defense and it does that badly, which is why FIP exists, but the unearned run rule still moves a lot of ERA leaderboards.
At Little League and travel ball. Youth scorebooks record enormous error totals and they are close to meaningless, because ordinary effort for a nine year old is not a defined thing. What matters at that level is which errors: a throwing error from the outfield tells you about arm and decision, a booted routine grounder tells you about feet, and the fixes are completely different drills.
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