A metric that determines the number of runs an offensive player produces for his team. This number is scaled so an "average" hitter has a wRAA of zero.
The wRAA metric is calculated using another advanced statistic, Weighted On-Base Average (wOBA). Weighted On-Base Average takes each possible outcome of an at-bat into account, and weights each event by the likelihood the event will lead to run production. Once this is known, we can determine what the wRAA would be for that particular player.
Weighted Runs Above Average is a number that accumulates over the course of a season since it is based on total run production. This metric is calculated using an adjustment for different stadiums, since each venue has its own run-scoring level of difficulty. This adjustment allows us to compare any group of players, regardless of where they played their games, or what era they played in.
Among the all-time leaders in wRAA are Babe Ruth, Ted Williams, Barry Bonds, Ty Cobb, Stan Musial, Lou Gehrig, Hank Aaron, Tris Speaker, Willie Mays and Jimmie Foxx.