Ballparks & Home runs & numbers

I pulled some data from espn.com:

Ratio of (HR/AB at home) to (HR/AB on the road), by offense, 2005-2007

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Team                Park                                2005        2006        2007        Avg        Rel. Avg.
Baltimore        Oriole Park at Camden Yards        102.7%        159.5%        143.7%        135.3%        125.2%
Boston                Fenway Park                        91.8%        79.2%        93.1%        88.1%        81.5%
LA Angels        Angel Stadium of Anaheim        99.5%        80.0%        99.5%        93.0%        86.1%
Chicago Sox        US Cellular Field                146.0%        140.4%        144.8%        143.8%        133.1%
Cleveland        Jabobs Field                        84.8%        98.5%        140.8%        108.0%        100.0%
Detroit                Comerica Park                        115.3%        69.4%        133.4%        106.0%        98.1%
Kansas City        Kauffman Stadium                70.2%        112.2%        98.6%        93.7%        86.7%
Milwaukee        Miller Park                        117.9%        121.0%        116.1%        118.3%        109.5%
Minnesota        Metrodome                        105.4%        97.2%        71.3%        91.3%        84.5%
NY Yankees        Yankee Stadium                        126.6%        121.7%        116.9%        121.7%        112.7%
Oakland                McAfee Coliseum                        87.9%        97.5%        89.3%        91.6%        84.7%
Seattle                Safeco Field                        95.6%        97.5%        106.9%        100.0%        92.6%
Texas                Rangers Ballpark in Arlington        150.2%        105.4%        117.2%        124.2%        115.0%
Toronto                Rogers Center                        129.8%        157.0%        129.3%        138.7%        128.4%
Atlanta                Turner Field                        96.9%        85.5%        95.6%        92.7%        85.8%
Chicago Cubs        Wrigley Field                        108.1%        98.0%        127.7%        111.2%        103.0%
Cincinnati        Great American Ballpark                134.6%        139.8%        138.1%        137.5%        127.3%
Houston                Minute Maid Park                145.2%        138.0%        101.1%        128.1%        118.6%
LA Dodgers        Dodger Stadium                        125.2%        143.4%        119.2%        129.3%        119.6%
Washington        RFK Stadium                        71.9%        86.1%        67.1%        75.0%        69.4%
NY Mets                Shea Stadium                        93.6%        97.1%        95.7%        95.5%        88.4%
Philadelphia        Citizens Bank Park                133.6%        115.0%        127.4%        125.3%        116.0%
Pittsburgh        PNC Park                        76.3%        97.0%        82.0%        85.1%        78.8%
St. Louis        Busch Stadium                        123.2%        89.2%        82.0%        98.1%        90.8%
San Diego        PETCO Park                        76.1%        93.0%        80.8%        83.3%        77.1%
San Francisco        AT&T Park                        107.1%        62.6%        71.8%        80.5%        74.5%
Colorado        Coors Field                        129.3%        93.4%        152.5%        125.1%        115.8%
Florida                Dolphin Stadium                        85.6%        92.4%        121.8%        100.0%        92.5%
Arizona                Chase Field                        107.4%        119.9%        120.1%        115.8%        107.1%
Tampa Bay        Tropicana Field                        85.8%        117.6%        112.0%        105.1%        97.3%
Average                                                107.4%        104.5%        109.4%        107.1%        100.0%

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Ratio of (HR/AB at home) to (HR/AB on the road), by defense, 2005-2007

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Team                Park                                2005        2006        2007        Average        Rel. Avg.
Baltimore        Oriole Park at Camden Yards        90.2%        93.0%        100.0%        94.4%        99.9%
Boston                Fenway Park                        89.0%        66.5%        80.0%        78.5%        83.1%
LA Angels        Angel Stadium of Anaheim        84.7%        80.2%        78.1%        81.0%        85.7%
Chicago Sox        US Cellular Field                138.3%        116.0%        100.6%        118.3%        125.2%
Cleveland        Jabobs Field                        98.1%        79.3%        85.9%        87.8%        92.9%
Detroit                Comerica Park                        74.9%        94.8%        97.5%        89.1%        94.3%
Kansas City        Kauffman Stadium                76.5%        87.5%        84.0%        82.6%        87.5%
Milwaukee        Miller Park                        109.5%        84.7%        111.9%        102.1%        108.0%
Minnesota        Metrodome                        89.8%        74.6%        75.7%        80.0%        84.7%
NY Yankees        Yankee Stadium                        88.9%        98.9%        112.4%        100.1%        105.9%
Oakland                McAfee Coliseum                        90.8%        75.3%        73.1%        79.8%        84.4%
Seattle                Safeco Field                        71.3%        87.9%        96.6%        85.3%        90.3%
Texas                Rangers Ballpark in Arlington        96.1%        103.2%        81.4%        93.6%        99.0%
Toronto                Rogers Center                        119.2%        96.8%        111.8%        109.3%        115.7%
Atlanta                Turner Field                        77.7%        104.1%        103.6%        95.1%        100.7%
Chicago Cubs        Wrigley Field                        99.7%        140.7%        97.6%        112.7%        119.2%
Cincinnati        Great American Ballpark                111.0%        118.2%        128.2%        119.1%        126.1%
Houston                Minute Maid Park                100.2%        101.2%        103.7%        101.7%        107.6%
LA Dodgers        Dodger Stadium                        95.3%        103.2%        91.7%        96.7%        102.4%
Washington        RFK Stadium                        87.8%        84.8%        68.0%        80.2%        84.9%
NY Mets                Shea Stadium                        83.0%        79.7%        89.8%        84.2%        89.1%
Philadelphia        Citizens Bank Park                120.3%        130.6%        168.9%        140.0%        148.1%
Pittsburgh        PNC Park                        92.0%        62.9%        75.9%        76.9%        81.4%
St. Louis        Busch Stadium                        107.8%        86.2%        63.2%        85.7%        90.8%
San Diego        PETCO Park                        76.8%        104.4%        60.6%        80.6%        85.3%
San Francisco        AT&T Park                        81.5%        76.5%        83.7%        80.6%        85.3%
Colorado        Coors Field                        84.0%        139.5%        93.2%        105.6%        111.8%
Florida                Dolphin Stadium                        79.7%        86.8%        75.2%        80.5%        85.3%
Arizona                Chase Field                        101.1%        146.2%        103.3%        116.8%        123.7%
Tampa Bay        Tropicana Field                        88.4%        117.4%        83.4%        96.4%        102.0%
Average                                                93.0%        95.7%        91.4%        93.4%        100.0%

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For example looking at the Twins in 2005, the first table indicates Twin batters hit 1.057 HR/AB in the Metrodome for every HR/AB they hit on the road. Twins' pitchers gave up only .898 HR/AB in the dome for every HR/AB they allowed on the road. (Pitchers AB's were constructed from total bases allowed divided by slugging avg. against). Note the data tells you nothing about how many home runs a team hit or gave up in total, just how many at home versus on the road.

The "average" column is just the three-year unweighted average, and the "relative avg" column is the team's three-year average divided by the total mlb three-year average.

I think St. Louis got a new park in 2006, so the 2005 numbers for them aren't too relevant. Looks like they may have gone from a hitters park to a pitchers park.

It looks like the strongest parks for hitters (concerning HRs only) are US Cellular (ChiSox); Rogers Center (Tor); Great American (Cin); and Citizens Bank (Phi). For pitchers, the best parks for HRs were: RFK (Was); AT&T (SF); PNC (Pit); and Fenway (Bos).

My goal was to determine if the data back up the idea that some parks are "hitter's parks" versus "pitcher's parks" and if so get some idea of how big the park effects are. There is a lot more volatility from season to seaon than I expected.

Some of the numbers are weird. Baltimore and Texas hit a lot more home runs at home than they do on the road, but their pitchers don't give up a lot more. Atlanta and the Cubs are just they opposite; they almost seem to have a home field disadvantage in terms of HRs. Colorado is just a mystery; I know they use the humidor, which is supposed to compensate for the elevation/dry air. I don't know how to interpret those numbers at all.