Personal Park Effects (Part 1)
There's been a lot of talk on this site about park effects, as Eric Walker and Sky Andrecheck just this week delved into home-field advantage, precision, and accuracy.
My idea is that not all park effects are uniform. For example, I believe that Mike Lowell and Dustin Pedroia are largely aided by the Green Monster, to a greater extent than most hitters and Johnny Damon's home run production has been largely influenced by the short porch in Yankee Stadium's right field. So what I've set out to do is use Hit Tracker data to compare players' home runs at home and away from home, and perhaps come to conclusions about certain ballparks effects on certain players.
I will not attempt to come up with my own home run factors. One reason for this is because if I look at only home runs here, I will face terrible selective sampling issues which would make my results neither precise nor accurate. The other is that I'm not that smart. I'll just present the data, and try to infer results from it. For actual park effects, Walker linked to a paper by my friends at the Harvard Sports Analysis Collective, and in the future I will be referring to a couple of articles at The Hardball Times by David Gassko and Greg Rybarczyk.
Here are the averages for all regular season home runs from 2006-2008 for which Hit Tracker has information. Here is the glossary for the terms. I've broken the fields into left, center, and right. I'd love to get more granular if I had more data. The second column refers to how many home runs were hit over the timespan, and the percentage hit to each field. The rest are Hit Tracker terms.
I defined the dimensions so that 12% of balls went out to center, so as to be consistent with the work I did last week. However, Hit Tracker also gives horizontal launch angles, with which you can define your own dimensions rather accurately. As there are more right-handed batters than left-handed batters, there are more left-field home runs than right-field home runs. Other than that, the differences between left and right are negligible. Homers to center are hit harder and farther, but also need more help from atmospheric effects. On to specific ballparks. Click on the ballpark names to view their dimensions.
Homers in Arlington certainly travel. They have by far the greatest impact from temperature of any ballpark. There have actually been more home runs to right field than left, which would likely mean that it is easier to hit home runs in that direction. Indeed, home runs to right have to travel a lesser distance than those to left. This is likely compounded by the home team, the Texas Rangers, trying to exploit this advantage by stocking up on lefties or switch-hitters. This effect is most prominent with the Yankees and Yankee Stadium, who have been well-known to go after left-handed batters as their production will be enhanced by the short right-field fences.
Angels Stadium seems to play true to most of the league averages. It might be a bit easier than normal to hit home runs out to center.
I'm surprised that AT&T Park has one of the strongest negative temperature effects. I guess being by the bay really cools the weather. This, and an endemic offense from the home team, contribute to the very small amount of homers to have been hit in AT&T. However, the wind will ratchet up at times. It's clearly a pitcher's park. I imagine it would have been helpful to break up this park into right-center and right field.
It can get windy in Busch, which will inflate the actual distances of home runs. Overall, the park is fair.
Chase Field is clearly a home run park, but it is quite deep to center. There aren't many cheap home runs hit at Chase.
Citizens Bank Park's dimensions are right around league average, but the walls don't just out toward right-center and left-center making home runs attainable in those directions.
Comerica is built for triples with its insanely deep walls in center field. Anyone who can hit homers out there is a man. For such a difficult home run park, its impressive how many homers have been hit there.
Mile-high air is worth 21 feet in home run distance. Aside from that, there's not much notable about the park. The deep fences do a decent job of canceling out the extreme altitude effects.
Dodger Stadium's center field doesn't reach 400 feet, so a rather high percentage of homers travel that way.
Dolphins Stadium is conducive to righties, so long as they can get some loft on their fly balls. Right field is the opposite, as home runs travel farther but not as high. Straightaway center is 400 feet, which is normal, but the walls jut out from there, making home runs into the power alleys difficult. Fly balls are aided by the temperature, though I'm not sure the temperature data accounts for whatever effect humidity might cause.
You can see how high home runs have to go to clear the Green Monster. Though the relationship is far from strict, ten feet in distance correlates with an extra foot and a half in apex height. But in Fenway, homers to center are 40 feet longer but only half a foot higher on average than those to left.
Great American seems to be a bit harder on righties than it is to lefties, but it overall plays as a home run hitter's park.
I would think that it shouldn't be too hard to hit balls out of the Jake to center, but there haven't been too many hit in that direction for some reason.
Looking at the atmospheric effects, I'm surprised it's so difficult to hit home runs at Kauffman, though the fences are kind of deep to right-center and left-center field.
I always thought McAfee was a more difficult home run park, but the dimensions aren't bad at all. It does have the worst wind and temperature effects of any park, though.
It takes some elevation to hit home runs over the baggy in right, but there are a lot of cheap home runs hit in that direction too. A 32.9 degree elevation angle is the highest figure for any field I came up with and 370 feet in standard distance is the lowest to a field either direction of center.
Down the line to right is nice and short. The apex of home runs to center is unusual.
That hill out in center sure makes things difficult for power hitters. It's unusual that the wind had an adverse effect on center-field home runs, since normally balls need a little help from the wind to carry that far.
There's not much of a sample for Nationals Park, but it seems to play around league average, unlike RFK which was cavernous.
Oriole Park is definitely a home run haven thanks to friendly atmospherics and a short fence in left.
Petco is death to righties. Wind might blow from left to right in Petco more often than not. Straightaway center isn't so deep, but the fences in the alleys extend out to 400 feet.
PNC plays similarly to Petco, except it is even harder on righties and even easier out to center. Jason Bay must be happy getting out of that ballpark and into Fenway where he can pepper the left-field wall.
I almost feel bad for Nationals hitters who had to play in this behemoth of a stadium.
It's impressive that there was an above average amount of home runs in the Rogers Centre and also above average distances.
Safeco is awful for right-handed power hitters. It was an odd decision for the Mariners to go after Adrian Beltre and Richie Sexson.
If you thought Shea Stadium was a pitcher's park, wait until you see how Citi Field plays.
The Trop conforms to league averages except to center where the walls are very deep.
Turner Field is deep down the lines, but hitters get a lot of help from altitude, wind, and temperature.
I had always thought that there was a jet stream of wind that forced balls out of U.S. Cellular, but it appears that the park is friendly to home runs only because of the crazy-short fences. The deepest part of the park might not even reach 390 feet.
Wrigley Field is windy, who would've guessed? I don't think that the park has much to do with the Cubs' decision to stock up on right-handed bats.
There's been a lot of talk about the new Yankee Stadium playing like a bandbox, but the old stadium wasn't so bad itself. The short right-field porch allowed the Yankees to stack up on lefties, so there has been a higher percentage of homers hit to right in Yankee Stadium than any other park.
Why is Fenway and Dolphin stadium the same?
Posted by: Chris at April 21, 2009 10:19 AM
It looks like Hit Tracker has the horizontal angle of each HR. Could you use that to make the data more granular?
Posted by: Dave Allen at April 21, 2009 10:43 AM
Chris, good catch. Should be fixed.
Dave, 500+ homers is enough data to make the data more granular. However, for these purposes I will be looking at individual players who will have hit at most about 100 home runs, so I wasn't sure whether It would be wise to split it up into more than 3 fields. I'm going to want to be comparing apples to apples when I look at individual players.
Posted by: Jeremy Greenhouse at April 21, 2009 1:19 PM
I would have probably missed anyways, but Fenway and Dolphins staidum aren't too different, both having a high but not too far left field fence, a triangle of sorts in deep center and a short fence in right that needs powerful line drives rather than towering flyballs to get it out. The only big difference is the wind, temperatures and humidity, which are quite different.
Posted by: Alex at April 21, 2009 9:33 PM
The Rangers don't play in Ameriquest Field -- it is Rangers Ballpark in Arlington.
Posted by: WonkoTheSane at April 21, 2009 9:50 PM
Wonko, thanks for stopping by. The ballpark has been called Ameriquest Field, and for the sake of consistency I left that as the park's title.
Posted by: Jeremy Greenhouse at April 21, 2009 10:13 PM
Could you please explain what the category "parks" means? If it's in the glossary, I don't see it.
Posted by: Brendan Scolari at April 21, 2009 10:50 PM
Sorry about that Brandon. Parks means the average number of parks a home run would have left. It was a determining factor in how easy it is to hit it out to a certain dimension. For example, a home run hit to center field in Comerica Park on average would leave 28.9 parks. This means that it is easier to hit home runs to center in other parks than it is to hit them in Comerica. On the other hand, a home run to center field in Angels stadium would leave 15.1 parks. This means that on average half of the parks in the league would contain those balls, so those home runs or lucky (or, it is relatively easy to hit home runs to center field in Angels Stadium).
Posted by: Jeremy Greenhouse at April 21, 2009 11:04 PM