Baseball Hacks

OBP, SLG, and Scoring Runs

Calculate the relative strengths of how you can use OBP and SLG to estimate runs.

In his 2003 best-selling book, Moneyball (W. W. Norton & Company), Michael Lewis communicated that in the evaluation of players, the Oakland Athletics organization placed a weight on on-base percentage that was worth roughly three times the weight of slugging percentage:

…OPS was the simple addition of on-base and slugging percentages. Crude as it was, it was a much better indicator than any other offensive statistic of the number of runs a team would score. Simply adding the two statistics together, however, implied that they were of equal importance. If the goal was to raise a team’s OPS, an extra percentage point of on-base was as good as an extra percentage point of slugging.

Before his thought experiment Paul [DePodesta] had felt uneasy with this crude assumption; now he saw that the assumption was absurd. An extra point of on-base percentage was clearly more valuable than an extra point of slugging percentage—but by how much? … In his model an extra point of on-base percentage was worth three times an extra point of slugging percentage.

In this hack, we’ll show how to calculate how much more important OBP is than SLG, using a simple linear regression analysis. And we’ll demonstrate that this number is closer to two than it is to three.

The Data and the Code

In this hack, we take a very simple approach to calculating the relative values of OBP and SLG, as they pertain to ...