Baseball is always going to be a game of volatility. Players are going to go into streaks of making outs, and then all of the sudden start hitting again, before they stop for a little bit. Luck plays an underrated factor in the way the game is played. However, some players are able to moderate that volatility. Derek Jeter is the best at it.
Bill Petti over at Fangraphs wrote today about the VOL statistic, which measures standard deviations in day-to-day hitting performances measured by wOBA. Basically, it measures how concentrated a player’s hitting contributions are. A player who almost always goes 1 for 4 or 1 for 3 with a walk, etc but rarely goes 4 for 5 with 2 extra base hits will have a lower VOL than a player who has a lot of punchless days but occasionally strings together a lot of big hits.
Derek Jeter not only led the league in VOL in 2012, but also is the career league leader since 1974. I don’t think it surprises any Yankee fans to know that Derek Jeter is very consistent, but its news to me that he’s probably the most consistent player of my lifetime. That he is also a really good hitter overall is a separate issue, but consistency helps explain it.
Petti explains the usefulness of VOL:
The one bit of inferential analysis I’ve completed was a look at the year to year correlation of VOL. Turns out, this new formulation has a higher correlation year to year than my previous one (.39 vs. .23). Overall, it’s still low — basically, it’s as reliable year to year as batting average — but there is a decent relationship and we do see evidence in the data that, like BABIP, over the course of a career players will sort by generally higher or lower VOL. For example, the correlation between a hitter’s average VOL for years one and two and a hitter’s volatility in year 3 is .42. This is something that definitely needs to be examined further, which brings me to next steps.
Well, there is a lot to do.
First, I want to look at what traits might lead a hitter to be more or less volatile. From my earlier research, and observations from others, my initial guess is high on-base, low strikeout, solid contact hitters will tend to have lower volatility. From the initial leader boards I am seeing these might still be the most significant variables, but of course it needs to be verified empirically.
Second, there is the larger question of whether the volatility of hitters matters all that much. How does it factor in to team construction? There is evidence that more consistent offenses tend to perform better over the course of the year (i.e. beat their pythagorean expectation in terms of wins), but the relationship between individual-level volatility and team-level volatility still needs to be addressed.
I’ll add one more: I’d love to see the metric applied to minor league players. I know that’s pie in the sky, but my hunch is that VOL would be a pretty good predictor of who is going to make a splash in the major leagues.