The Ale-X-Files: wOBA, A Primer

The Ale-X-Files are a regular article that will focus on statistical aspects and patterns in the ABL.

This week, I wanted to take a look at a relatively new statistic (relative to other baseball stats) that has become one of my favorite tools for evaluating hitters: wOBA, or Weighted-On-Base-Average.

wOBA attempts to calculate a player's overall value as a hitter in a single number (that is then scaled to look like OBP).

This statistic was developed by Tom Tango and popularized in his book, The Book: Playing the Percentages in Baseball, so much of what you read here is paraphrased from that source.  For anyone interested in statistics, I'd highly recommend The Book.

This week is a a primer for what wOBA is.   As mentioned, I'll be regularly including it in other articles in the series.

Editorial Note: I fully realize that some people are turned off (or on) by newer statistics for various reasons, or that they're somewhat inaccessible due to the math involved.  That's fine, but please take and use this summary for whatever you think it might be worth.  The biggest reason I'm introducing it here is that it will be a stat that I regularly refer to in this series.


There are a couple of important keys to understanding why a stat like wOBA is useful as well as what wOBA is.  Let's start with why wOBA is needed:

• Current individual numbers, OBP, SLG, and OPS, are flawed to some degree.  This isn't to say they are bad stats, but that individually they don't tell a good story of a hitter's success (or lack thereof). Here's a quick summary.
• OBP: while the stat that most correlates with runs scored, says nothing about the method by which the player reached, a walk and HR are counted the same.
• SLG:  While attempting to weigh the number of bases, doesn't do so properly.  For example, a single is weighted 1/4 as much as HR.  Additionally, it ignores walks.
• OPS:  If you've ever mismeasured two boards that need to be placed together you know that two flaws tend to create a larger mistake, and that's the issue with OPS.

The key components to understanding wOBA:

• Run Expectancy and Run Value are the basic currency of wOBA (Note, this is relatively simplified version. If you want more details, there are plenty of sources for this)  .  In baseball, every event in a baseball game is tracked and, thanks to computers and modern media, the exact number of runs scored after that event occurs in an inning every game over the course an entire season can be calculated.  
• For example, you can take all the doubles that were hit in a particular season or multiple sesaons, figure out how many runs were scored after the double occurred until the inning ending and then average it out p/double.  The number for doubles in modern baseball is around 1.08 (based on Tango's calculations in the book).
• wOBA then uses these run values of HR, 3B, 2B, 1B, HBP, and NIBB and divides them by plate appearances and then converted into a number that scales similar to OBP.
• The league average for wOBA is around .330.  (I'll be taking a look at this for the ABL)

Here are the current top five hitters in wOBA, and I'm guessing there won't be many surprises (min PA 200):

Lorenzo Rodriguez .506 (staggering!)   

Steve Frend .469

Tom Becker .462

Peter Blanchard .462

Steven Jackson .417