MLB Park Factors
Our fantasy hamsters are busy spinning their activity wheel to produce a nice MLB Park Factors page, but the real 411 insiders know to get it here on the blog, so
here it is!
What do these numbers mean, how did we determine them? Glad you asked!
* We added up the batting stats compiled by the home team in all games in their home ballpark over the past three seasons (2006-07 for the new Busch Stadium), PLUS the stats compiled by their opponents in those games;
* Then, we added up the batting stats for each team and their opponents in their road games… that is to say, we took all Diamondbacks home batting stats (plus their opponents in home games) and compared them to their road batting stats (plus their opponents in road games);
* Next, we pro-rated all stats over 1,000 plate appearances so we’d be comparing the frequency of events on a per-plate-appearance basis, rather than simply counting up to see where something happened the most, which could be skewed if hitters had more PA’s in one ballpark than another;
* Then, we divided the prorated home stats by the prorated road stats to determine an index for each stat category. Keep in mind that some ballparks may increase production in one category, but decrease it in others, so providing only a single value isn’t a great way to determine the influence of each park on offensive production.
The numbers provided here are “simple” park factors, meaning that these numbers are not adjust edfor strength of schedule. That is, the Pirates may play the Red Sox in interleague play while the Cardinals play the Orioles, and the relative strength of those opponents will somewhat skew the frequency with which different offensive events occur. Our friends at Baseball Prospectus do this, which results in some slightly different numbers, but for basic fantasy purposes the “simple” method is still very useful and telling.
Here’s a for instance… the Chase Field HR factor is 114, meaning the Diamondbacks and their opponents hit 14% more homers in Chase Field over the past three years than they did on the road. And while Fenway Park is actually not a good homer park (83), it increases doubles (135) more than enough to offset that, making it a good offensive park overall in terms of runs per game (108) and OPS (102).
Another interesting tidbit is the effect of parks on stolen base attempts and success rate… note that many of the parks perceived as bad hitters’ parks have above-average rates of stolen base attempts, perhaps as teams attempt to compensate for the tougher environment by running more. But what’s also interesting is that (with smaller variation than other stats, but still) some parks lead to higher SB success rates that others… for instance, PNC Park saw 3% more SB attempts than road games, but allowed 8% less in terms of success rate. What causes this? Infield types? Different types of materials? Wet track? I wonder how we can find out more about this to figure out where our sleeper basestealers would come from…
OK, that’s it, enjoy. Looking forward to reading questions and comments!