Is Bonds hitting in the wrong park?

AT&T Park, the home field of the San Francisco Giants, may be among the worst places for hitting home runs. According to my analysis of the 2000 to 2005 seasons, only the San Diego Padres' PETCO Park rates worse. How many more home runs might Barry Bonds have hit playing his home games somewhere else?

A while back, Evan asked about home run ball parks. The burning question there was, do the Rangers and Reds play in better homer parks than the Rockies? I think the answer is no.

I looked at AB/HR for both pitchers and batters both at home and on the road over the last six seasons, using data from Retrosheet. (For teams that have changed home parks, only the seasons in their current park are included.) I computed the ratio of road AB/HR to home AB/HR. A value larger than one means it takes more at bats to hit a home run on the road, while a value less than one means it takes fewer. So the team with the highest ratio seems to have the best homer ball park.

AB/HR Road vs. Home Ratio

Team	Batting	Pitching	Total
Colorado Rockies	1.46	1.23	1.34
Chicago White Sox	1.46	1.16	1.31
Philadelphia Phillies	1.23	1.15	1.19
Cincinnati Reds	1.17	1.17	1.17
Texas Rangers	1.31	1.02	1.16
Houston Astros	1.18	1.09	1.14
Milwaukee Brewers	1.08	1.13	1.11
New York Yankees	1.17	1.02	1.10
Toronto Blue Jays	1.16	1.03	1.10
Arizona Diamondbacks	1.09	1.09	1.09
Chicago Cubs	1.08	1.01	1.05
Los Angeles Dodgers	1.08	1.01	1.04
Baltimore Orioles	1.05	1.01	1.03
Oakland Athletics	1.13	0.91	1.02
Atlanta Braves	1.01	0.95	0.98
Kansas City Royals	0.96	0.98	0.98
St. Louis Cardinals	1.01	0.91	0.96
Anaheim Angels	1.05	0.87	0.96
Cleveland Indians	0.98	0.93	0.95
Tampa Bay Devil Rays	0.91	0.91	0.92
Seattle Mariners	0.97	0.84	0.90
Minnesota Twins	0.90	0.88	0.89
Boston Red Sox	0.89	0.88	0.88
Pittsburgh Pirates	0.90	0.85	0.88
New York Mets	0.92	0.83	0.87
Florida Marlins	0.93	0.78	0.85
Washington Nationals	0.72	0.88	0.81
Detroit Tigers	0.84	0.73	0.78
San Francisco Giants	0.85	0.69	0.77
San Diego Padres	0.76	0.71	0.74

Here's a visualization of the Batting vs. Pitching ratios, which demonstrates a pretty strong correlation between them. (Note that this includes a few extra data points, which are the old parks of the teams that have moved.)The fact that the batting ratio is usually above the line means that hitters are affected more by going on the road than pitchers.

The data suggest that the Rockies and White Sox have the best parks for hitting home runs in, while the Padres and Giants have the worst.

Unfortunately, this analysis is not without its problems. The unbalanced schedule presents one, because the road statistics are strongly influenced by the division. Also, while several teams have nearly identical ratios for batting and pitching, others are not so close, including San Francisco. The Giants pitchers seem to enjoy the biggest home field advantage of any team, but their batting is fourth from the bottom, at about 0.85. This type of anomaly may have to do with differences in difficulty for lefty and righty batters. A more thorough analysis would account for both of these factors. Any suggestions?

Still, I think this is a clear improvement over simple counting of home runs in various ball parks over the same period.