Measure how many runs a player would contribute to an average team with RC.
Runs created, or RC, is a measurement of the number of runs an offensive player contributed to a team during a season. Bill James developed this formula over time, publishing an initial version in his book 1979 Baseball Abstract. (This book has been out of print for some time. See http://baseballanalysts.com/archives/2004/07/abstracts_from_14.php for a description of the contents.)
Run creation is a neat idea. Traditional statistics such as runs scored (R) and runs batted in (RBI) count the number of times a player did something. These are good measurements in one way because they measure what actually happened in a game. But they depend on context.
Suppose there is a league average player, whom we will call Joe Average. During one season, Joe is on a lousy team. When Joe hits the ball, players rarely are on base, so Joe gets few RBIs. After Joe reaches base, the other players rarely hit the ball, so Joe gets few runs.
Now suppose that in a different season, Joe is on a great team. When Joe hits the ball, players often are on base, so Joe gets many RBIs. After Joe reaches base, the other players often hit the ball, so Joe scores many runs.
Clearly, Joe’s teammates help him out greatly. When his teammates hit better, Joe bats in more runs and scores more runs. We’d like to develop a statistic to measure how much Joe contributes to winning, independent of his teammates’ performance. ...