Thursday, November 5, 2009

The Best Bandbox

Recently I was downloading some data for a project that I have planned relating to park factor, when I had a moment of inspiration. It occurred to me that one could get a rough idea of how easy it is to hit a home run, at a given stadium, simply by finding the percentage of batted balls that were home runs. In other words, dividing the number of home runs by the number of AB's where the batter did not strike out would yield a home run rate. The higher the rate, the easier it is to hit home runs. The equation is simple and looks like this:

R=HR/(AB-K)

Before doing this, my belief was that Coors field would not ave the highest rate. I also had a suspicion that a certain stadium would have the highest rate. So I ran the numbers, looking at both the home team's and away teams' home run rate for each stadium in 2009. Here are the results:

ClubStadiumTeamOpponentsTotal
NYYYankee Stadium III5.96%4.61%5.30%
TEXRangers Ballpark in Arlington5.80%4.02%4.87%
PHICitizens Bank Park5.02%4.42%4.71%
MILMiller Park4.83%4.55%4.69%
CHAComiskey Park II4.77%4.03%4.40%
TORSkyDome4.67%4.07%4.37%
CINGreat American Ballpark4.46%4.20%4.33%
TAMTropicana Field4.97%3.70%4.31%
BOSFenway Park5.38%3.26%4.30%
BALOriole Park at Camden Yards4.15%4.42%4.29%
LAAAngel Stadium of Anaheim4.01%4.53%4.27%
DETComerica Park4.26%3.98%4.12%
MINHubert H. Humphrey Metrodome4.22%3.87%4.04%
ARIChase Field4.07%3.82%3.94%
COLCoors Field4.59%3.30%3.93%
FLADolphin Stadium3.99%3.74%3.87%
MLB Average4.00%3.63%3.81%
CHNWrigley Field3.87%3.74%3.80%
HOUMinute Maid Park3.57%3.84%3.71%
WASNationals Park3.57%3.57%3.57%
SEASafeco Field3.50%3.51%3.51%
OAKNetwork Associates Coliseum3.25%3.07%3.16%
PITPNC Park3.39%2.92%3.15%
SDGPetCo Park3.05%3.16%3.11%
SFGAT&T Park3.11%3.07%3.09%
CLEJacobs Field3.10%3.05%3.07%
KANKauffman Stadium2.87%3.01%2.94%
LADDodger Stadium3.18%2.68%2.94%
NYMCiti Field2.22%3.61%2.92%
ATLTurner Field3.18%2.55%2.87%
STLBusch Stadium II3.06%2.41%2.73%

As you can see, the new Yankee Stadium comes out on top, with 5.3% of batted balls hit here turning into home runs. So that's it, the new Yankee Stadium is the easiest place to hit it out. Coors Field, as I guessed, was not really an easy place to hit home home runs. Unfortunately it's not that simple. These results may have more to do with each team's ability to hit home runs, and of their pitching staff's inability to keep the ball in the yard. So a team with lot of power and poor pitching is likely to score high on this list.

So in order to adjust for a team's ability, a new value must be found. The first step that I took was to recalculate the above table for each team while on the road. The following table shows these rates:

ClubTeamOpponentsTotal
PHI5.10%4.09%4.61%
CLE4.27%4.89%4.58%
TAM4.45%4.62%4.54%
BOS4.25%4.40%4.32%
NYY4.57%3.86%4.23%
TOR4.30%4.13%4.22%
MIL3.71%4.69%4.21%
DET4.02%4.27%4.14%
TEX4.70%3.58%4.14%
KAN3.63%4.65%4.13%
SDG3.56%4.55%4.05%
SEA3.69%4.23%3.95%
COL4.63%3.24%3.92%
ARI4.04%3.76%3.89%
WAS3.71%3.90%3.80%
BAL2.79%4.79%3.78%
MLB Average3.63%3.83%3.73%
MIN3.28%4.17%3.72%
STL4.15%3.18%3.67%
CHA3.55%3.66%3.60%
CIN2.88%4.27%3.57%
FLA3.33%3.72%3.52%
LAA3.57%3.45%3.51%
HOU2.83%4.21%3.50%
CHN3.62%4.01%3.39%
LAD3.23%3.45%3.33%
OAK2.72%3.90%3.29%
ATL3.47%3.02%3.25%
PIT2.42%3.89%3.17%
SFG2.54%3.83%3.14%
NYM1.98%3.47%2.71%

In this table it can be seen that the Phillies had the highest rate of batted balls becoming home runs. This was largely due to their ability to hit home runs at a high rate. While on the road, 5.1% of batted balls by the Phillies became home runs. While at home, only 5.02% of their batted balls were home runs. Their opponenets did benefit by playing in Philly, with 4.42% of batted balls at the Bank becoming home runs and only 4.09% becoming home runs in Phillies' away games.

The next step is to divide the data in the two tables to determine the increase (or decrease) in rate of home runs to batted balls when a team is in it's home park. If there is an increase in thee ratios when playing at home, then playing in that stadium is beneficial to hitting home runs. The following table shows the ratios:

ClubStadiumTeamOpponentsTotal
NYYYankee Stadium III1.30561.19621.2519
CHAComiskey Park II1.34161.10341.2201
LAAAngel Stadium of Anaheim1.12401.31481.2180
CINGreat American Ballpark1.54950.98561.2118
TEXRangers Ballpark in Arlington1.23301.12521.1769
BALOriole Park at Camden Yards1.49030.92301.1341
CHNWrigley Field1.06780.93341.1240
MILMiller Park1.30140.97041.1140
FLADolphin Stadium1.20001.00601.0988
MINHubert H. Humphrey Metrodome1.28590.92641.0865
NYMCiti Field1.12031.03931.0776
HOUMinute Maid Park1.26110.91291.0592
TORSkyDome1.08660.98501.0360
PHICitizens Bank Park0.98381.07891.0229
MLB Average1.10260.94691.0220
ARIChase Field1.00831.01661.0115
COLCoors Field0.99191.01831.0022
PITPNC Park1.40160.75240.9945
BOSFenway Park1.26650.74040.9943
DETComerica Park1.05960.93250.9942
SFGAT&T Park1.22550.80250.9834
OAKNetwork Associates Coliseum1.19730.78750.9600
TAMTropicana Field1.11690.80090.9511
WASNationals Park0.96430.91620.9393
SEASafeco Field0.94810.83100.8870
LADDodger Stadium0.98510.77830.8815
ATLTurner Field0.91570.84620.8812
SDGPetCo Park0.85760.69420.7679
STLBusch Stadium II0.73730.75890.7429
KANKauffman Stadium0.78970.64600.7110
CLEJacobs Field0.72570.62390.6706

As it turns out, new Yankee Stadium is the easiest stadium in the Major Leagues to hit a home run, with 25.19% more batted balls landing in the seats than in Yankee away games. Although Yankee Stadium provided the biggest increase in home run rate, the Yankees didn't benefit as much as some other teams. The rate of home runs was 55% higher at home for the Cincinnatti Reds than when they were on the road. Their opponents actually hit homeruns at a slightly lesser rate, when coming into Great American Ballpark. As it turns out, the Rockies had a tougher time in 2009 hitting home runs while on the road, than while at Coors. Their opponents did benefit slightly, but overall the rate was nearly the same as in away games.

This analysis provides a new look on whether or not a stadium really is a good home run park or not. Unlike park factor, which only considers the amount of homeruns per game, this method looks deeper and find the number of homeruns per batted ball. This is important since other factors may lead to increased number of plate appearances per game, in certain stadiums. The additional plate appearances add to the number of homeruns, thus slightly inflating the home run park factor. Like park factor, there is still a flaw which I will discuss further in a future post. Until then, hopefully I have shed some light on which ballparks really are home run friendly and which are not.