I've always been fascinated by park effects. I think it is one of the great unexplored areas left in sabermetrics, along with defense and contextual effects. One thing that some fans lament about the O.co is the large foul territory and how it affects the offense. Now, I don't have (nor do I think one is available) an easily accessible measure of percentage of playing field that is foul territory; that would be ideal. One potentially surrogate measure, though, is BABIP. That is to say, BABIP may be correlated with team offense one way or another.
I used FanGraphs and B-R home-away splits to construct a table of team BABIPs and team wOBAs from 2002-2011. From there, I used BABIP as the independent variable in an XY scatter plot, and found the correlation coefficient using the Trendline function.
|BABIP/wOBA - Home||0.05|
|BABIP/wOBA - Away||
(I would put the graphs in, but they just look silly)
As you can see, there appears to be no correlation at home between wOBA and BABIP. That is to say, as BABIP increases, it is not influencing wOBA. There is a slightly larger, but still relatively small correlation between Away BABIP and Away wOBA. That is to say, to a greater extent than at home, team BABIP may increase team wOBA.
One interpretation of these data are to say that, given the O.co’s large foul territory, a greater percentage of balls in play end up being foul balls, thereby negating any effects of actually putting the ball in play.
Another would be to say that the A’s simply hit better at home, BABIP be damned. Indeed, there is a well-known home field advantage in baseball (Hello, 2011 Brewers!). Given that the inverse is also true (teams perform worse on the road), the A’s may be more at the mercy of BABIP to power their offense.