Footnotes
- a This is shown in the mathematical formula at right.
- b Recognized "major leagues" include the current American and National Leagues and several defunct leagues—the American Association, the Federal League, the Players' League, and the Union Association.
- c A pitcher must throw a minimum of one inning per game scheduled for his team during the season (currently 162 innings per 162 games) to qualify for the ERA title.
Read more about this topic: List Of Major League Baseball Earned Run Average Champions