An Offensive Earned-Run Average for Baseball

This paper studies a baseball statistic that plays the role of an offensive earned-run average (OERA). The OERA of an individual is simply the number of earned runs per game that he would score if he batted in all nine positions in the line-up. Evaluation can be performed by hand by scoring the sequence of times at bat of a given batter. This statistic has the obvious natural interpretation and tends to evaluate strictly personal rather than team achievement. Some theoretical properties of this statistic are developed, and we give our answer to the question, “Who is the greatest hitter in baseball history?”