Valuing Offense: The Elegant Simplicity of wOBA

Ever since "Moneyball" was published, there have been two lines of thoughts on walks. On one hand, the sabermetrically-inclined have harped upon how valuable walks are; on the other, traditionalists have stuck by their guns, claiming that, "A walk isn't as good as a hit!" Saberists have rebutted the argument, pointing out how there are a limited number of outs in a game and good players don't make outs...and calling the other person a dumb-bat in the process. The traditionalists followed with a shot across the bow and a right hook to the face, and hence the enmity between the two camps grew.

And so, I'm here today to settle the debate once and for all: is a walk as good as a hit? No, it is not. Walks are good and they're better than making an out, but a walk isn't as valuable as a single because singles have the potential to move runners multiple bases at a time. This is a marginal difference, considering that there aren't always runners on base and both instances still get you a runner on first, but a difference nonetheless. Traditionalists, you were right.

Similarly, not all hits are created equal. This makes intuitive sense to us; a homerun is more valuable than a single, for instance. If you had to choose between two players with the same batting averages but one player hit 40 homeruns and the other 5 homeruns, you'd take the player that hit 40 homeruns in a heartbeat, right? Singles are more valuable than walks, doubles are more valuable than singles, triples more valuable than doubles, and homeruns are more valuable than all of them. I don't think you'll find any baseball fans disputing this fact - again, it's common sense.

The question, then, is how much better? Say you have these two players and you need to determine which one of them is a more valuable offensive player:

Player A: 190 hits, 150 singles, 30 doubles, 2 triples, 8 homeruns, 100 BB, 0 HBP, .333 BA

Player B: 190 hits, 130 singles, 35 doubles, 0 triples, 25 homeruns, 25 BB, 0 HBP, .333 BA

Which player is more valuable? Does Player B's extra power make up for his lack of walks? How valuable are Player A's triples in comparison with Player B's doubles? Is a double worth exactly twice the amount of value as a single? Is a triple exactly three times the value of a single? Slugging percentage would have you believe it's that simple, but where's the proof? Here's my favorite question again: why is that true? Is it?

These are the sort of questions that plagued saberists for a number of years, until someone (Tom Tango, I believe) decided to run some empirical tests and establish - once and for all - the value of different offensive outcomes. Once these values had been established, it was just an extra step to turn the results into a formula that weighed each offensive event for its proper value. This statistic is called Weighted On-Base Average (wOBA) and it's the greatest thing since sliced bread. So now, instead of looking at oodles and oddles of numbers to determine who is a more valuable hitter, we can just look at a final number like this:

Player A: .392 wOBA

Player B: .381 wOBA

Oh, so Player A's walks did make up for his lack of power, and he was the more valuable player. Simple, huh? That's the basic premise behind wOBA: it's one statistic that encapsulates a player's offensive performance. Think of it like OPS, but only more accurate because real mathematicians came up with the proper values for each hit. Some versions of wOBA (like the version over at FanGraphs) include stolen bases in their calculations, giving players added value if they steal bases at a high rate of success. Weighted One-Base Average is scaled to look like On-Base Percentage, with league-average coming in around .335. Just like with OBP, a wOBA of .400 is quite high and a wOBA below .300 is horrendously low.

And this is why I love wOBA - that's all there is to it! I don't know how the mathematicians established the proper weights, but I don't need to; that's their job. This is a statistic that says, "Okay, so we know that singles are more valuable than walks, doubles are more valuable than singles, triples more valuable than doubles, and homeruns are more valuable than all of them. I'll do all the work for you and show you how productive your player has been in one simple, easy-to-understand stat. Okie dokie?"

If you're still attached to batting average, OBP, SLG%, and OPS, that's fine. They're perfectly good statistics, but realize that each of them only gives you a small piece to the puzzle. Only wOBA puts the puzzle pieces together for you.

For more on wOBA, check out its page at The Sabermetrics Library or ask questions below. Also, for those of you that like more hands-on experience, feel free to play around with this wOBA calculator. Put in different inputs and watch how the wOBAs change.