From SABR member Kevin Johnson at Seamheads.com on April 30, 2012:
The Seamheads.com Ballparks Database has now been updated with 2011 data plus the latest and greatest corrections.
As a reminder, we provide two sets of calculations: 1-year factors and 3-year factors.
The 1-year factors are observed factors, based on only the season in question. While we do use an other parks corrector as described in the detail documentation, these are essentially the factors that were observed for that particular year, so a 120 doubles factor for LH batters in Fenway Park means that left-handed batters hit 20% more doubles at Fenway than LH batters for those same teams’ batters hit in games away from Fenway.
The 3-year factors are attempts at calculating “truer” factors. There are many, many ways we could have constructed our formula, and it’s difficult to determine what the “best” way is, but we believe our way is at least a good and defensible way. Our basic formula is to use the 1-year factors for the season in question, the season immediately preceding, the season immediately following, and then the park’s long-term historical factor, all weighted equally. As some parks have rather long histories, while other may have life for only a few seasons, this is not a perfect method, but we believe it retains a basic simplicity while providing for a high degree of accuracy in estimating a park’s impact on offensive events.
We welcome any feedback on any of the data or suggestions for improvement, so try it out and enjoy!
Read the full article here: http://seamheads.com/2012/04/30/ballparks-database-updated-2/
Originally published: May 1, 2012. Last Updated: May 1, 2012.