You should not pay attention to park factors using just one year of data, but here some are!
Throughout the summer months, the Safeco Field run-suppression was talked about as often as if it were its own player on the team. It started out in a typical "golly gee can the Mariners not score runs, again," manner, but then the conversation shifted when it was noticed that road teams in Safeco couldn't score either. And so it became a fascination on how nobody could score and various theories started flying, foremost among them was the prolonged Spring weather.
Regardless of the cause, the cries for a change in park dimensions reached perhaps a new high. At least, it was a new well-supported high. They may have been more proponents of it back when the Mariners actually had fans that went to games and cared. And when it seemed like it couldn't stay this bad, like Chone Figgins, it just kept being that bad, like Chone Figgins. Changing the dimensions became a big topic at the summer meet-up with the Mariners brass.
The fascination waned a bit down the stretch as the Mariners managed to post a roughly league average offense in September/October, for whatever tens of reasons. Plus the announcement of the fences moving changed the focus more toward how much that will affect things for next year rather than looking back on the past season.
I had commented a couple times throughout the season how the park factors were looking, as my rolling three-year window started including more and more 2012 data and the runs factor just kept falling. What I never did was compute park factors using only this year's data. I didn't do it because single year park factors are dumb.
But lately, I've been tinkering with my park factor equations a bit and since I was mucking around in a test environment, I decided this was a perfect opportunity to actually do those 2012-only park factors, just to see how they looked. Here's how they looked.
Single year park factors are silly. They're as silly as a rabbit chasing after a duck. How silly! What is the rabbit thinking? Or the duck? Haha. But unlike a rabbit chasing after a duck, you shouldn't look at single year park factors. The margins of error are so big that they dwarf the numbers. A while back, I looked at confidence intervals for three-year factors. They're pretty big! Now consider it with one-third of the sample size. Do you get how silly one-year factors are now?
So do not, please, do not, take the numbers above as if they are 100% accurate. They come with enormous error bars. Everything, really, comes with error bars and people just tend to totally ignore that, but you really should not ignore it here because these are very big error bars. They are so big that I'm not even classifying this post as a "Stats" post because I think that implies too much weightiness to the numbers.
The columns you're probably interested in are the final two, covering home runs and runs overall. You should ignore completely the home run one because of the margin of error is probably like +/- 60. The runs isn't much more precise, but for the sake of translating such a pitching-friendly factor into context, I'm going to treat it like it is accurate. The 2012 Mariners scored 257 runs at home and 362 on the road. Adjusting the home total for these one-year factors would bring it up from 257 to 299, a 42-run increase. That's over half a run for the Mariners in every home game!
Except not, because these aren't meaningful. Don't read meaning into a rabbit chasing a duck or into these numbers.