KEEPING SCORE; Viewing Baseball Through a Prism of the Numbers
By SEAN FORMAN
Published: April 16, 2010
Sean Forman is the creator of Baseball-Reference.com, an online baseball encyclopedia of players, teams and box scores in the major and minor leagues.
Sabermetrics at its core is an attempt to measure the value added by baseball players. It is intensely concerned with accurately assigning credit or blame for what happens on the field.
This has value not only in ranking players for what they have done, but also in predicting which players are most likely to contribute wins and losses. Traditional statistics like batting average, runs batted in, wins, losses and earned run average certainly give us some of the picture. But they do not present the whole picture, a big reason sabermetrics has gained such wide acceptance in the major leagues.
For example, the player who hits the sacrifice fly is credited with an R.B.I., but no credit is assigned to the batter whose double moved the runner to third, a much more valuable act.
So today we begin publishing an alternative leader board. Using 2009 numbers, we will begin with four statistics: one batting, one pitching, one fielding and one overall team statistic (expanded numbers appear at bbref.com/nytimes/).
Batting Runs are a creation of Pete Palmer, an editor of many baseball encyclopedias, and are an attempt to measure all of a batter's positives and negatives: hits (even if they don't score a run), walks, hit-by-pitch and outs. The ultimate run-scoring value of each of these events has been researched - for example, a double is typically worth 0.85 runs. We then add up the value of each batter's events and create adjustments for the hitting environment by era and by park, so a performance in Coors Field in 2000, a hitter's park, can be compared to one in Dodger Stadium in 1968, a pitcher's heaven. The statistic is presented as runs generated when compared to a league-average batter.
E.R.A.+ is a little bit simpler. It takes the league-average E.R.A. adjusted to the ballpark, divides it by the pitcher's E.R.A. and multiplies by 100. So 100 would be exactly league average and more than 100 is better than average.
Total Zone is a new defensive metric created by Sean Smith. It considers the outcome and location of every ball hit into play, then works out how a fielder did relative to his peers. The end figure is the number of runs a player saves or costs his team. Total Zone does not consider fly balls caught by infielders or throws scooped by the first baseman.
Simple Rating System goes beyond wins and losses, combining each team's margin of victory and strength of schedule to determine how many runs better than average the rated team is. For example, last year's Yankees were 1.26 runs a game better than average. This translates to a 100-win team, which is just about where the Yankees were.