Historical Trends in Home-Field Advantage

 

by Cyril Morong

Email


Click here to see my sabermetric blog called Cybermetrics

 

 

This paper was published in the Baseball Research Journal, from the Socitey for American Baseball Research. Special thanks to David Smith for providing me all the necessary data from the Retrosheet files

 

From 1901-2002, the average seasonal difference between a teamís home winning percentage and its road winning percentage was .082.1 But has it changed much over the last 100 years and has the change been significant? What teams have enjoyed an especially good home field advantage?

††††††††††† Figure 1 shows how the average home field advantage changed from 1901-2002.

Now, there is a slight downward trend over the century, but quite a bit of year-to-year variance. The average home advantage in 1931 was .164, and then fell rapidly and dramatically afterwards.Then there is the huge spike to .146 in 1978, the biggest advantage since 1931.A decade-by-decade summary might be a little more interesting.This is given in Table 12which clearly shows that the home field advantage has declined over time.Yet the second decade has the second lowest average.So there is a trend, but anomalies as well. Has the change been statistically significant?Yes.3 But is it significant in a baseball sense?When the average advantage is .103, it means a home winning percentage of about .552.When the advantage is .07, it means a home winning percentage of .535.This difference over 81 games is 1.36 wins.I leave it to each reader to decide if that is significant in a baseball sense. The third column projects how many more games a team would win at home above an even split. For example, in the first decade an even split would give a home team 38.5 wins.But with a .1042 difference between their home and road percentages (a .552 home winning percentage), they would win 42.51 games at home.Decades from the 1960ís on use 81 games.

Table 1

Decade

Average

Advantage

Extra Home Wins

for Full Season

1901-10

0.1042

4.01

1911-20

0.0740

2.85

1921-30

0.0928

3.57

1931-40

0.0976

3.76

1941-50

0.0922

3.55

1951-60

0.0784

3.02

1961-70

0.0796

3.22

1971-80

0.0752

3.05

1981-90

0.0800

3.24

1991-2002

0.0700

2.84

 

Home stands are not as long as they used to be and teams now travel by plane.This might account for the historical trend.But notice that the difference between the 1940ís and 1950ís is not too great and that the 1980ís was higher than the 1970ís. The average from 1901-1950 was .091 and since it has been .076.This seems like a small difference.

††††††††††† Table 2 shows the top teams in each decade. A team had to play at least five years in the decade to qualify.4

†††††† †††† Table 2

Decade

Leader

Advantage

Extra Home Wins

for Full Season

1901-10

Philadelphia (AL)

0.2289

8.81

1911-20

Brooklyn

0.0936

3.60

1921-30

Cincinnati

0.1277

4.92

1931-40

Cleveland

0.1183

4.55

1941-50

Boston (AL)

0.1947

7.50

1951-60

Cincinnati

0.1113

4.29

1961-70

Houston

0.1895

7.67

1971-80

Houston

0.1202

4.87

1981-90

Minnesota

0.1731

7.01

1991-2002

Colorado

0.1658

6.71

 

Table 3 shows the top ten teams since 1901 that existed in one city for at least ten years.Changes in ballparks for these teams was not taken into account. (Table 3 assumes an 81 game home schedule for all teams).

†† †††††††† Table 3

Team

Advantage

Extra Home Wins

for Full Season

Rockies

0.1433

5.80

Marlins

0.1216

4.92

Astros

0.1190

4.82

Athletics-Phi.

0.1077

4.36

Red Sox

0.1045

4.23

Browns

0.0942

3.81

1st Senators

0.0911

3.69

Braves-Bos.

0.0910

3.69

Giants-SF

0.0900

3.65

Yankees

0.0881

3.57

 

The lowest home advantage belongs to the Orioles, at .051.

Has a big home field advantage been an aid?Not really. The overall winning percentage of the teams with the twenty-five highest single-season home advantages is .492. For the twenty-five worst teams it is .498. The only one of the best twenty-five to win a pennant was the 1987 Twins. Table 4 shows the best ten home field advantages since 1901. It uses the 77 home game and 81 home game schedules where appropriate.

††††† ††††† †††Table 4

Team

Year

Advantage

Extra Home Wins

for Full Season

Philadelphia (AL)

1945

0.356

13.71

Philadelphia (AL)

1902

0.338

13.01

Boston (AL)

1949

0.337

12.97

Colorado

1996

0.333

13.49

Minnesota

1987

0.333

13.49

Houston

1978

0.321

13.00

Philadelphia (AL)

1908

0.319

12.28

Chicago (AL)

1903

0.315

12.13

Chicago (AL)

1902

0.312

12.01

Boston (AL)

1952

0.311

11.97

 

Despite the trend towards a lower home field advantage, 2003 saw a fairly big one.The average home field advantage was .099. There were also seven teams that had at least a .160 advantage, which is just about twice the historical average.With 23.33% of the teams being above the .160 mark, this is the highest percentage since 1986 when seven of the twenty-six teams were above .160. This past season was the 29th highest percentage of teams going above .160.Table 5 shows the home advantage for all teams in 2003.

††† ††††††††††††††††††††††††††††††† Table 5

Team

Advantage

Home W

Home L

Road W

Road L

Colorado

0.296

49

32

25

56

Montreal

0.259

52

29

31

50

Oakland

0.222

57

24

39

42

Chi White Sox

0.198

51

30

35

46

Texas

0.185

43

38

28

53

Florida

0.185

53

28

38

43

San Francisco

0.166

57

24

43

37

Anaheim

0.149

45

37

32

48

Philadelphia

0.148

49

32

37

44

Boston

0.136

53

28

42

39

St. Louis

0.136

48

33

37

44

Baltimore

0.122

40

40

31

51

Atlanta

0.111

55

26

46

35

Tampa Bay

0.111

36

45

27

54

Houston

0.111

48

33

39

42

Cleveland

0.099

38

43

30

51

Los Angeles

0.086

46

35

39

42

Seattle

0.086

50

31

43

38

Arizona

0.074

45

36

39

42

Minnesota

0.074

48

33

42

39

San Diego

0.074

35

46

29

52

Detroit

0.037

23

58

20

61

Pittsburgh

0.037

39

42

36

45

NY Mets

0.030

34

46

32

49

Cincinnati

0.012

35

46

34

47

Chi Cubs

0.000

44

37

44

37

Kansas City

-0.024

40

40

43

39

NY Yankees

-0.028

50

32

51

29

Toronto

-0.049

41

40

45

36

Milwaukee

-0.074

31

50

37

44

 

Notes

1.This is just a simple average, adding up every teamís single season advantage and dividing by the number team-seasons.Season with longer schedules are not given extra weight.

 

2. Again, this is just a simple average.The overall home field advantage is added up for each of the ten seasons and then is divided by ten.Seasons with more teams or games donít get extra weight. The low figure for the 1911-20 period is not affected much by the Federal League, which had a about a .084 advantage during its two seasons.

 

3. Using the means test, the difference between the first decade and the last is significant, with a Z-score of 3.97. Also, here is the standard deviation for all teams for each decade: 0.0914, 0.0848, 0.0769, 0.0787, 0.0857, 0.0855, 0.0831, 0.0837, 0.0773, 0.0810. This shows that the dispersion in home field advantage across teams has not changed much since 1901. The correlation between year and the average yearly home advantage is -.247. It has a t-value of Ė2.55, which iss statistically significant.

 

4. The advantage listed for teams that changed parks in their respective decade only includes data from the park they played the most seasons in.Only one of those teams, the Indians of the 1930ís, actually did not have the biggest advantage when only their most commonly used stadium was considered. The Reds would then actually be a little higher, at .1188. The following are the teams that changed parks and their home advantage for the entire decade:Philadelphia (01-10), .2021; Cleveland (31-40), .1234; Houston (61-70), .1783; Minnesota (81-90), .1438; Colorado (91-2002), .1433. For all of them, except Cleveland, they would still have the highest yearly average even if all years of the decade are used.

 

Sources

Retrosheet generated data from David Smith, head of Retrosheet.

 

Yahoo! Major League Baseball Web Site

 

STATS INC. All-Time Baseball Sourcebook


Back to Cyril Morong's Sabermetric Research