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December 31, 2010

Ahead in the Count

What Home Teams Do Better

by Matt Swartz

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A few weeks ago, I wrote about how home teams had improved their performance in the last three years. After winning about 54 percent of games consistently for the last 60 years, home teams have won 55.5 percent of games in the last three seasons. Although it is just a 1.5 percent increase, there has not been a three-year period with home team winning percentage this high in 60 years, so there may be a noticeable reason for the shift.

Last time, I looked through which teams had seen the biggest home-field advantages in recent years, but there is little, if any, variation between teams in their abilities to win a disproportionate share of games at home. That is why in this article I have taken a different approach and looked at home and away performances in individual statistics over the last three years and compared them to the 1993-2007 period in which there has been a similar run environment to 2008-2010 (4.82 versus 4.55 runs per game), but a smaller home-field advantage (53.6 versus 55.5 percent).

Despite the larger home-field advantage overall, neither strikeouts nor walks appear to be happening more frequently.

Statistic

Home

Away

Diff.

% Change at Home

SO/PA% 1993-2007

16.1

17.0

-0.91

5.34

SO/PA% 2008-2010

17.5

18.5

-1.01

5.44

BB/PA% 1993-2007

9.12

8.46

0.66

7.80

BB/PA% 2008-2010

9.02

8.39

0.64

7.60

There has barely been any change in how pitchers and hitters work counts at home and on the road. Pitchers continue to strike out a little more than five percent more hitters while walking a little less than eight percent fewer batters at home.

Home runs are a different story, as there has been a sharp change in how frequently batters hit the ball out of the park at home.

Statistic

Home

Away

Diff.

% Change at Home

HR/AB% 1993-2007

3.16

3.04

0.12

3.97

HR/AB% 2008-2010

3.06

2.79

0.27

9.83

Home teams hit more home runs than road teams by more than twice the margin in the last three years than they did in the previous 15 seasons. Why is this? Could this be that hitters are seeing the ball better at their own parks? Are hitters better matched for their parks? To consider possibilities such as these, I also looked at several other statistics to consider the difference in recent years.

Statistic

Home

Away

Diff.

% Change at Home

BABIP 1993-2007

.302

.295

.0063

2.15

BABIP 2008-2010

.303

.295

.0084

2.86

This does not appear to be extremely different, though there is definitely a tendency for hitters to do better at getting hits on balls in play at their own park, and more so in the last three years than the previous years. What types of hits are occurring more frequently?

Statistic

Home

Away

Diff.

% Change at Home

Singles/100 BIP 1993-2007

22.71

22.29

0.43

1.91

Singles/100 BIP 2008-2010

22.66

22.13

0.53

2.40

Doubles/100 BIP 1993-2007

6.68

6.58

0.10

1.55

Doubles/100 BIP 2008-2010

6.86

7.72

0.14

2.04

Triples/100 BIP 1993-2007

0.77

0.66

0.11

16.01

Triples/100 BIP 2008-2010

0.79

0.61

0.17

28.28

There has been a major change in triples both home and away, while the increase in home-team doubles has been relatively minor, as has the change in the home-team singles. Triples have always been a statistic that shows a large home-field advantage, because they usually involve outfielders misplaying bounces, which occurs more often to defenders unfamiliar with the stadium they are playing in. The extra triples for home teams combined with the much fewer three-baggers for road teams suggests that clubs are starting to play better in their own parks.

The larger home-field advantage increase appears to have occurred in home runs and triples, which suggests that teams have players better-suited to their home parks or that players are playing their home parks better. Given the plethora of data available on spray charts, teams may be acquiring players whose fly balls are particularly likely to leave their parks, finding players who can take advantage of misplays in their stadiums, and outfielders who avoid misplays of their own.

The following table lists a few other statistics’ difference in home and road performance in recent years.

Statistic

Home

Away

Diff.

% Change at Home

AVG 1993-2007

.271

.263

.009

3.28

AVG 2008-2010

.267

.256

.011

4.49

OBP 1993-2007

.343

.330

.013

3.85

OBP 2008-2010

.338

.323

.015

4.78

SLG 1993-2007

.431

.416

.015

3.69

SLG 2008-2010

.425

.401

.024

6.00

ROE/100 BIP 1993-2007

1.49

1.48

0.00

0.22

ROE/100 BIP 2008-2010

1.37

1.31

0.05

4.12

Reach/BIP 1993-2007

.317

.310

.006

2.05

Reach/BIP 2008-2010

.317

.308

.009

2.91

GDP/(SI+BB+HBP) 1993-2007

.078

.082

-.004

-4.86

GDP/(SI+BB+HBP) 2008-2010

.080

.083

-.003

3.90

SB% 1993-2007

70.5

68.4

2.06

3.02

SB% 2008-2010

73.0

72.2

0.79

1.09

HBP/100 PA 1993-2007

.0089

.0086

.0003

3.41

HBP/100 PA 2008-2010

.0089

.0083

.0007

8.12

More players have reached on errors at home in recent years, which could be about defense or more scrutinized scoring decisions. The latter explanation could explain the relatively smaller jump in singles.

Most other statistics do not show much change. The advantage at stealing bases at home has actually shrunk in the last three years, while fewer road pitchers are hitting batters than in previous years. Players are grounding into double plays at a similar clip as well.

Overall, this data combines to paint the general picture that the main difference in home-field advantage in recent years is success on contact, particularly in mashing home runs and triples. This still does not provide a definitive answer as to whether home teams are doing something different that will allow them to continue winning more often, or whether we should expect a reversion to the 54 percent rate we have seen throughout history. However, the fact that there have been large changes in home runs and triples as opposed to a series of small changes in many statistics suggests that something major may have changed, and provides evidence of a shift in home-field advantage that I did not see in my article before.

 What do you think? Do the statistics above suggest home-field advantage will continue to grow? 

Matt Swartz is an author of Baseball Prospectus. 
Click here to see Matt's other articles. You can contact Matt by clicking here

6 comments have been left for this article.

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