Friday, July 27, 2007

Runs Created Update

One of my favorite summary stats for hitters is Runs Created (RC). RC is an estimate of a team's runs which were produced by an individual player. Runs created is calculated from the number of walks, singles, doubles, triples, homeruns and other things that a player does to score runs. Bill James showed in his Baseball Abstracts many years ago that runs created is highly correlated with runs scored. This tells us that runs scored are essentially the sum of other team statistics and are not, in general, accounted for by unmeasured factors. There are many runs created formulas but they all have the same basic structure:

RC= (A*B)/C

where A= number of runners on base, B=advancement of runners and C=opportunities to do A and B.

One of the first runs created formulas was developed by Bill James in 1979. It was simply:

RC= ((hits+walks)*total bases)/(ab+walks).


This version is still useful for some purposes but the formula has evolved over the years and more recent versions are more accurate in estimating runs scored. Sabermetrician DanFox gave a brief history of runs created on his blog. The RC figures presented here were abstracted from the ESPN database. I believe the formula they use is:


RC = (((2.4*C+A)*(3*C+B))/(9*C))-(.9*C)


where

A = H+BB+HBP-CS-GIDP
B = TB+.24*(BB-IBB+HBP)+.62*SB+.5*(SH+SF)-.03*SO
C = AB+BB+HBP+SH+SF


Table 1 below lists the RC for Detroit Tigers batters and where they rank among American League regulars as of July 26.

Table 1: RC for Detroit Tigers as of July 26

League Rank

Player

RC

2

Ordonez

86.3

3

Granderson

80.5

5

Sheffield

79.9

21

Guillen

63.0

25

Polanco

61.3

65

Inge

45.4

70

Casey

43.5

81

Rodriguez

39.7

109

Monroe

29.3

125

Thames

21.6


As you can see, the Tigers have 3 players in the top 5 and 5 in the top 25 so it's no surprise that they lead the league in runs scored.

RC favors players who play in a lot of games. This is not a bad thing but sometimes we want to know the rate in which a player creastes runs in games that he does play. For this, we have Runs Created per 27 outs (RC27). For example, Magglio Ordonez has 9.06 RC27. Theoretically, this means that a team of 9 Magglio Ordonez's would score 9.06 runs per game. Table 2 lists the RC27 figures for Tigers and how they rank among 90 American League regulars with 3.1 or more plate appearances per game.

Table 2: RC27 for Detroit Tigers as of July 26

League

Rank

Player

RC27

2

Ordonez

9.06

7

Sheffield

8.02

9

Granderson

7.73

20

Guillen

6.83

27

Polanco

6.42

49

Casey

5.25

57

Inge

4.86

77

Rodriguez

4.27

88

Monroe

3.16

--

Thames

4.70

2 comments:

  1. Table 2 appears to be a duplicate of Table 1.

    ReplyDelete
  2. Thanks Matt. I fixed it.

    Lee

    ReplyDelete

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