Last day we’ll deal with this, I promise.
I probably should have included in yesterday’s column
was a brief
explanation of how park factors are calculated. A lot of the mail I
received attempted to tie Veterans Stadium’s high walk park factor to the
composition of the Phillies’ staff. While that seems to make intuitive
sense–and is a common misconception–it is not the case.
A park factor is not influenced in any significant way by a team’s
abilities. Park factors compare the results of the games played in a team’s
home park to the results of that team’s road games. Park factors include
all the statistics generated by both teams; that is, the performance of the
Phillies in their 72 (see note below) home games against NL teams counts
just as much as the performance of the opponents in those games. The totals
in those games are compared to the totals in all of the Phillies road games
to arrive at park factors for various occurrences.
(Note that STATS, Inc. only uses games within the league in calculating
park factors, surmising correctly that the differences in interleague
opponents would skew the factors.)
I can’t emphasize this point enough: park factors are independent of a
team’s composition. Having a good offense or a good pitching staff will not
skew a park factor, because the performance of that offense and that
pitching staff 1) accounts for only half the performance in a given park
and 2) is being compared to the performance against the same set of
opponents in the rest of the league.
As an extreme example, let’s look at the San Francisco Giants in 2000. The
Giants finished third in the league in runs scored, and first in runs
scored on the road (in NL games). They had the best offense in the league
as measured by Equivalent Average. If a team’s performance can have an
undue influence on park factor, we would expect that Pacific Bell Park
would seems like a hitters’ park, or at least a neutral one.
Pacific Bell Park was the third-best pitchers’ park in the NL last year.
The Giants and their opponents combined for 672 runs in 72 games at the
Bell (9.3 per game), and a whopping 831 in 75 games on the road (11.1 per
As far as the Phillies are concerned, their pitchers walked 305 hitters at
the Vet, and just 258 away from it. Their batters walked 278 times at home,
and 261 times on the road. The totals of 583 walks in Philadelphia and 519
elsewhere on the continent yield a walk park factor of 110. The large gap
between the Phillies’ pitchers totals at the Vet and on the road suggests
that the staff isn’t the driving factor. They walked more batters in home
games than all but two other teams (the Pirates and Brewers), but were 12th
in the NL in walks allowed on the road.
I don’t want to dwell too much on the Phillies, or on any specific pieces
of data. The point I want to emphasize is that park factors are real, and
not subject to influence by a team’s characteristics.
Finally, did anyone else think it was cool that Barry Bonds‘s 500th
home run was about as clutch as they come, turning 1-2 into 3-2 and a
possible loss into a win? Bonds has taken far too much grief over the years
for his postseason performance, while not getting enough credit for the
otherworldly Septembers that have carried his teams to the
postseason. That he got to be a hero with everyone’s eyes on him was a
Joe Sheehan is an author of Baseball Prospectus. Contact him by