Wyers: The philosophy of park factors

From SABR member Colin Wyers at Baseball Prospectus on December 21, 2012:

There was some chatter on Twitter this morning about park factors, and Marc Normandin made the point that all of the most common park-adjusted offensive stats out there (TAv, OPS+, wRC+) use “generic” run-based park factors, not component park factors. (Baseball Prospectus does have component park factors which we use in PECOTA, and we use those to generate our run-based park factors, but we use run-based park factors in TAv.) Marc wondered if using one-size-fits-all rather than the component factors leads to inaccuracies might — after all, we know different parks affect different types of hitters in different ways, and our park adjustment methods here don’t account for that. (Marc’s not the first to raise this point, by the way.) So why do we all do it this way?

The answer is not, as you might suspect, additional complexity — at least not for us here at Baseball Prospectus. We generate lines based on component park adjustments daily for in-season PECOTA anyway. No, this is a deliberate choice to park adjust TAv the way we do.

Read the full article here: http://www.baseballprospectus.com/article.php?articleid=19239

Originally published: December 21, 2012. Last Updated: December 21, 2012.