Double-Parked

Dave Paisley

In my last article I took a peek at National League park effects to date. There were quite a few weird anomalies there, and believe me, the American league is no different. If anything, it's a bit weirder.

Just as a refresher, let me remind you that the term "Park Effect" is primarily used to quantify how easy it is to score runs in a particular ballpark relative to the other ballparks in the league. Ballparks affect different aspects of the game in different ways, but the ultimate determination of park effect always seems to come down to how easy is it to score runs there. In the American League, one of the most recent stories has been the Mariners' new park, Safeco Field. The conventional wisdom is that it is heavily biased to being a pitcher's park, but the real story is a lot more curious than that.

Before I get into specifics, let me describe the following table to you. It's pretty much the same as the one I showed for the NL except that it shows AL numbers, hence it's two teams shorter, leaving room for league averages. Apart from that, it's the same. It shows the runs each team scores per home game and road game, then how many runs their opponents have scored per home game and per road game.

The table then shows the park factor, i.e., the ratio of runs per game at home to runs per game on the road. Next up is park factor for the opponents, i.e., ditto, except it's for the opponents. Finally, the overall park factor (what you will most often seen referred to as "The Park Factor") combines home and visitor factors to measure how easy it is for both teams to score runs in this park. The table is arranged from highest overall park factor to lowest.

Team	R/G Home	R/G Road	R/G by Opp Home	R/G by Opp Road	Park Factor Home Team	Park Factor Road Team	Overall Park Factor
Tex	6.28	4.53	5.88	5.57	1.39	1.06	1.20
Min	5.11	4.37	5.79	5.00	1.17	1.16	1.16
Ana	5.83	4.86	5.40	5.16	1.20	1.05	1.12
Tor	5.71	5.21	6.15	5.48	1.09	1.12	1.11
Chi	6.40	5.81	5.24	5.24	1.10	1.00	1.05
Bos	5.10	5.11	4.82	4.44	1.00	1.09	1.04
KC	5.29	5.39	6.21	5.79	.98	1.07	1.03
Cle	5.68	5.57	5.24	5.13	1.02	1.02	1.02
NY	5.51	5.60	4.94	4.66	.98	1.06	1.02
Det	4.76	4.66	5.14	5.45	1.02	.94	.98
TB	4.30	5.44	5.85	5.19	.79	1.13	.95
Bal	5.26	5.13	5.45	6.46	1.03	.84	.92
Oak	5.46	6.42	4.91	5.69	.85	.86	.86
Sea	5.50	5.90	3.77	5.44	.93	.69	.82
Average	5.44	5.29	5.34	1.04	1.01	1.02

It's no shock that The Ballpark at Arlington tops the list. It's been a perennial hitter's park since it opened, and has inflated the MVP statistics of many an undeserved Texas MVP to be sure. Even more curious, though, is the fact that it helps the home team by a huge amount (+39%), whereas it barely helps their opponents at all (a mere +6%.)

So much like many NL parks, we find that "park factor" isn't necessarily a park factor alone, inflating offense all around, it may just be that the home team has tailored itself to the ballpark. In recent years, though, offense at The Ballpark has been inflated by less than 10% overall, and last year, Rangers' opponents did much better in Arlington than on the road, while the Rangers did about the equally well in both places.

On the other hand, the next team on the list is the Twins. Here, offense is equally inflated by home and road teams alike, to the tune of +16% or so. Last year, offense was up 13% in the dome, but the average of the past three years has been just 4% over average. So much for those patterns again.

One of the big stories earlier this year was the massive offense at Skydome. Apparently, runs were flowing, the ball was flying out, it was one big offensive party. People were asking what funny additives the government of Ontario was adding to the water. Other than the usual ones, of course.

Well, the answer is that whatever it was, it was helping the opposition more than the Blue Jays. The Jays have scored 5.71 runs per game at home, while their opponents have managed a whopping 6.15. Jays fans will tell you that it's just the "Roy Halladay effect" but I'm not sure it's so easily explained. Whatever it is, overall runs are up 11% versus league average, whereas the Dome has played pretty much neutral the last three years. Blame it on the Ritalin, I guess.

Meanwhile, what about Safeco Field? Sure, it ranks dead last in runs per game, but only because the Mariners' opponents have found it impossible to score much there. For the Mariners themselves, the park has only a marginally detrimental effect on scoring. The team is down 7% at home relative to their road game scoring. Opponents coming into the Safe, though, are down a whopping 31% in scoring. Like, ouch man, that hurts!

Here's another case where it's hard to believe that the park itself has some kind of overall depressive effect on scoring, but it only applies to the visiting team. Is it the psychological effect of teams visiting a park they've never seen before? OK, some of them saw it last year, but it's still pretty new to most players. This is really curious. If such a wide swing between home and road teams is possible, it call into question the whole notion of context-free park effects.

You can contrast Safeco with Oakland, a well-known defensive haven which is depressing home and visitor scoring equally, much as always. Then there's the Tampa Bay Devil Rays, with their home disadvantage. The Devil Rays suck to the tune of a .79 home park factor, while their opponents beat them like a drum for 13% more offense than in the Rays' road games. Now that's just ugly. Other teams with a home disadvantage are Boston (green pussycat, anyone?) Kansas City and the Yankees (hmmmm).

But so far for the Mariners, their new park has literally been "Safe at home". Not that I'm complaining...

It's no secret that Dave Paisley is a big fat Mariner fan. It was a surprise, however, when he arrived at the Strikethree.com offices one day with the Moose tattooed on his tush. Ask how we knew that in the first place at drdjp@strikethree.com.

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