AL Park Effects, Part II, Revisited

Dave Paisley

While gross park effects are interesting, for me there is a much more interesting story in how teams play at home and on the road. Which ballparks are tough on visiting teams. What is the average advantage of playing at home (and there certainly is one).

Gross park effects assume that home and road teams are equally effective or ineffective when playing in a given park, except for the generic home field advantage. What interests me is the difference between how teams take advantage of their home park, and how difficult that park can be for the visiting team.

Once again, I'm going to use OPS park effects rather than the more typical runs scored, as it's a more fundamentally pure measure of offense. if you haven't read it yet, go back and check out part one for the basic AL park factor story.

Now here's a different twist on the numbers. The next table shows Home OPS divided by Road OPS for the home team, and their combined opponents' OPS at that park divided by their OPS everywhere else. At the top of the heap, we have the Chicago White Sox, who took much better advantage of their home park than the rest of the league. Opponents were suppressed quite well, too.

Cleveland did very well at Jacobs Field, but so did their opponents. Same story for Texas. Toronto is an amazing story. Hitting 7% better at home than on the road, their opponents lost 11% when they went to SkyDome. So not only did the Jays do very well at home, their opponents die horrible deaths.

In the middle of the pack, the Yankees did 5% better at the House that Ruth Built, while suppressing their opponents by about 10%. Looking at the bottom of the list, Anaheim hit 8% worse at home than on the road, but we can't excuse that, as their opponents only hit 3% worse at the Big E.
 

Team	Team Home/Road OPS	Opponent Home/Road OPS
White Sox	1.103	.944
Indians	1.099	1.063
Rangers	1.096	1.045
Blue Jays	1.070	.892
Twins	1.065	.987
Red Sox	1.064	1.001
Mariners	1.048	.973
Yankees	1.047	.896
Royals	1.025	1.036
Devil Rays	.999	1.027
Orioles	.995	.897
Tigers	.991	1.022
Athletics	.961	.904
Angels	.924	.968
Average	1.035	.975

Note at the bottom, from the average home team and opponent numbers, we can see that there was approximately an 6% advantage in OPS to playing at home (1.035/.975). We can put this average advantage down to the traditional factors like home cooking and reduced travel.

I thought it would be even better to see how these ratios play out if we take the home team's ratio and divide it by the opponents' ratio, to determine just how much of a real advantage each team takes at home, by both generating offense themselves and suppressing the opposition's.
 
The first two columns of the next table are normalized by the home and road advantages. So a 1.000 in the home column would mean that it's getting exactly the average advantage from playing at home. A 1.000 in the opponent's column means that opponents are being allowed average performance in that park.

The final column is the ratio of the two ratios, and indicates just how much of an extra advantage a team got from playing at home.
 

Team	Adjusted Team Home/Road OPS	Adjusted Opponent Home/Road OPS	Team/ Opponent Adjusted OPS
Blue Jays	1.034	.915	1.130
Yankees	1.012	.918	1.102
White Sox	1.066	.968	1.102
Orioles	.962	.919	1.046
Twins	1.029	1.012	1.016
Mariners	1.013	.997	1.016
Athletics	.929	.927	1.002
Red Sox	1.028	1.027	1.001
Rangers	1.059	1.072	.988
Indians	1.062	1.090	.975
Royals	.991	1.062	.933
Devil Rays	.965	1.053	.917
Tigers	.957	1.048	.914
Angels	.893	.992	.900
Average	1.000	1.000	1.003

 
 We can see that on this basis, Toronto wins hands down with the Yankees and White Sox right behind. Baltimore is the only other team that got a significant advantage playing at home.

At the bottom of the table we have four teams that, well, suck anyway. The Royals, Devil Rays, and Tigers certainly. But what about those Angels, who got killed at home this year?

Note that despite all the hoopla about Texas and Cleveland being hitters' parks, the two teams actually lost out marginally to their opponents when playing at home.

Well, that's it for the AL park effects. Just wait till we get to the NL, with Coors to distort things,

 

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