The Phillies' Home: Fairest in the Land

Citizens Bank Park is a beautiful place to attend a game and has been recognized as such since opening in 2004. At the same time, it has been viewed by many players, and by most of the media, as a homerun haven and a park that greatly favors hitting.

Why? Small dimensions, and a penchant in its early years for boosting home runs (and to a much lesser extent, overall scoring). I'm sure there is a more mathematically correct way to do this, but if you add up CBP's 5 outfield distances (lines, alleys, and center) they are in aggregate the 2nd shortest in the majors.  Fenway is the only park with a shorter total, and it is the shortest everywhere but Center Field -- of course it also has the Green Monster in Left.  

It's not clear why CBP's dimensions have not translated into inflated scoring or home run numbers in recent years -- it may be due to wind effects, or that the phillies have tailored their pitching staff (but not their lineup?) to suit the park, etc.  But the bottom line is there are essentially no more runs scored, and no more home runs hit, in the Phillies' home games than there are in their away games.

And while "fairest" in the title may be stretching it, it's really not far from the truth.  Since the beginning of 2008, CBP has been one of the most neutral parks in baseball.  More after the break...

The Myth

There are often reports that list the number of homeruns hit in each park.  For example, after 2009 it was reported that there were 233 hit at CBP that year, 2nd only to Yankee Stadium, implying that CBP was the 2nd easiest to hit home runs in.  The non-saber-savvy media picks up on such reports, and the myth perpetuates.

What these reports fail to mention is that the team that plays its home games at CBP actually hit more home runs on the road than it did at home in 2009, and has hit only 3.6% more at home since 2008.  To translate this to a concrete example, if a player hit 57 homers, hitting 3.6% more at home would mean 29 at home, and 28 on the road. 

If CBP boosted homers as much as some people seem to think it does, the Phillies would own a few more records.  For example, U.S. Cellular Field in Chicago has boosted HRs 34.9% over the past 3 years.  In 2009 the Phillies hit 116 on the road -- if they had hit 34.9% more at home, they would have reached a total of 272, smashing the NL record (249 by the 2000 Astros), and even surpassing the MLB record of 264 (1997 Mariners).  Instead, they only hit 108 at home.

Park Factors

Just looking at total home runs "allowed" by a given stadium is misleading, because those numbers depend in large part on the home team's ability to hit them, and the ability of the staff to keep their opponents from doing the same. Which is why Park Factors were developed many years ago.  For the uninitiated, Park Factors are calculated by comparing stats in each team's home games with stats in their away games, in order to control for team-by-team differences. From ESPN's MLB Stats:

"Park Factor compares the rate of stats at home vs. the rate of stats on the road. A rate higher than 1.000 favors the hitter. Below 1.000 favors the pitcher. Teams with home games in multiple stadiums list aggregate Park Factors."  This is the calculation for Runs (RS=runs scored, RA=runs allowed):

"PF: ((homeRS + homeRA)/(homeG)) / ((roadRS + roadRA)/(roadG))"

This method still isn't perfect, because each team's set of away parks is different, especially when you factor in the unbalanced schedule, but it's certainly a step in the right direction.

Citizens Bank Park's Track Record 

There were years when CBP boosted home runs, including as recently as 2007. But even then, it reduced other types of hits, and as a result it boosted overall scoring only moderately.

However for the past 3 years, it's been one of the most neutral parks in MLB, both in terms of scoring in general, and homeruns in particular.

Year-by-year park factors and MLB rank:

Year PF Rank PF Rank
2004 1.024 12 1.134 5
2005 1.156 2 1.297 2
2006 1.063 8 1.201 6
2007 1.034 14 1.418 1
2008 1.029 15 1.022 11
2009 1.028 13 1.005 16
2010 .991 16 1.125 10

For 2008-2010 combined, the 3-year totals are:

  PF Rank   PF Rank
'08-10 1.015 12 1.042 12


3-Year Park Factors and Ranks

Below are the Park Factors and major league rank for each stadium, for 2008-2010:

COL 1.239 1 1.275 3 ATL 0.989 16 0.964 16
CHC 1.126 2 1.100 8 TOR 0.983 17 1.095 9
ARI 1.123 3 1.058 10 MIN 0.977 18 0.877 23
TEX 1.108 4 1.196 5 PIT 0.976 19 0.897 21
CHW 1.106 5 1.349 1 LAA 0.968 20   0.990 14
BOS 1.077 6   0.896 22     OAK 0.949 21 0.865 25
BAL 1.064 7 1.265 4 MIL 0.943 22 1.053 11
NYY 1.061 8 1.333 2 HOU 0.943 23 1.104 7
FLA 1.042 9 0.921 18 STL 0.933 24 0.806 28
DET 1.029 10   1.030 13     CLE 0.922 25 0.798 29
CIN 1.017 11 1.182 6 NYM 0.917 26   0.870 24
PHI 1.015 12 1.042 12 TAM 0.915 27 0.908 20
KC 1.015 13 0.819 27 SEA 0.899 28 0.823 26
SF 1.013 14 0.944 17 LAD 0.878 29 0.912 19
WAS 1.004 15 0.970 15 SD 0.802 30 0.768 30

- NYY and NYM are for 2009-2010 only
- MIN includes 2008-09 at the Metrodome, but based on just the one year's data, Target may be stingier, at least for HRs: 2010 PFs... Runs 0.962, HRs 0.641


The same data, graphically (click on the image to enlarge):


So the next time you hear what a great hitters' park CBP is, you'll know that the speaker is simply repeating what they've heard, without actually looking into the matter.

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