Home advantage of European major football leagues under COVID-19 pandemic

Presented at 8th Mathsport International Conference (https://sites.google.com/view/mathsportinternational8/home).

Abstract: Since March 2020, the environment surrounding football has changed dramatically because of the COVID-19 pandemic. After a few months' break, re-scheduled matches were held behind closed doors without spectators. The main objective of this study is a quantitative evaluation of “crowd effects” on home advantage, using the results of these closed matches.
The proposed analysis uses a pairwise comparison method to reduce the effects caused by the unbalanced schedule. The following conclusions were drawn from the statistical hypothesis tests conducted in this study: In four major European leagues, the home advantage is reduced in closed matches compared to than in the normal situation, i.e., with spectators. The reduction amounts among leagues were different. For example, in Germany, the home advantage was negative during the closed-match period. On the other hand, in England, statistically significant differences in home advantage were not observed between closed matches and normal situations.

Transcript

1. Home advantage of European major football leagues under COVID-19 pandemic EIJI KONAKA (MEIJO UNIVERSITY, JAPAN) MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
2. Outline ⚫Home advantage in football ⚫Closed match under COVID-19 pandemic ⚫Home advantage under COVID-19 pandemic ⚫Analysis method ⚫Results and discussions MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
3. Outline ⚫Home advantage in football ⚫Closed match under COVID-19 pandemic ⚫Home advantage under COVID-19 pandemic ⚫Analysis method ⚫Results and discussions MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
4. Home advantage in football ⚫“Home advantage” in sports ⚫“… the benefit that induces home teams to consistently win more than 50 percent of the games under a balanced home-and- away schedule.” [Courneya and Carron, 1992] ⚫Statistical survey over 120 football leagues over the world ⚫Source: https://www.worldfootball.net/ ⚫Summary (2010-2019) ⚫Matches: 173492 ⚫Home W/D/L 79648/43957/49887 ⚫Home GF/GA 260159/197531 ⚫Five major European leagues (ENG/GER/ITA/FRA/ESP) ⚫Matches: 16434 ⚫Home W/D/L 7550/4154/4730 ⚫Home GF/GA 25475/19151 MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
5. Home advantage in football ⚫“Home advantage” in sports ⚫“… the benefit that induces home teams to consistently win more than 50 percent of the games under a balanced home-and- away schedule.” [Courneya and Carron, 1992] ⚫Statistical survey over 120 football leagues over the world ⚫Source: https://www.worldfootball.net/ ⚫Summary (2010-2019) ⚫Matches: 173492 ⚫Home W/D/L ratio 0.4591/0.2534/0.2875 ⚫Home GF/GA ratio 0.5684/0.4316 ⚫Five major European leagues (ENG/GER/ITA/FRA/ESP) ⚫Matches: 16434 ⚫Home W/D/L ratio 0.4594/0.2528/0.2878 ⚫Home GF/GA ratio 0.5709/0.4291 MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Home advantage of five major European leagues is similar to the average all over the world
6. Home advantage in football: worldwide survey ⚫Statistical survey over 120 football leagues over the world ⚫Source: https://www.worldfootball. net/ ⚫2010-2019 ⚫Win prob. difference MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) World average
7. Home advantage in football: worldwide survey ⚫Statistical survey over 120 football leagues over the world ⚫Source: https://www.worldfootball. net/ ⚫2010-2019 ⚫Win prob. difference MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) World average
8. Home advantage in football: worldwide survey ⚫Statistical survey over 120 football leagues over the world ⚫Source: https://www.worldfootball. net/ ⚫2010-2019 ⚫Win prob. difference MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) World average
9. Home advantage in football: European major leagues ⚫Statistical survey ⚫Source: https://www.worldfootball. net/ ⚫2010-2019 ⚫Goals diff. per match ⚫Win prob. diff. ⚫Five major European leagues MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) World average World average
10. Explanations of home advantage ⚫Home advantage clearly exists in professional football. ⚫Possible causes of home advantage[Pollard 2008] ⚫Crowd effects, travel effects, familiarity, referee bias, territoriality, special tactics, rule factors, and their interactions. ⚫Key data ⚫Number of goals, yellow/red cards ⚫Most previous studies assumes a balanced schedule MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
11. Outline ⚫Home advantage in football ⚫Closed match under COVID-19 pandemic ⚫Home advantage under COVID-19 pandemic ⚫Analysis method ⚫Results and discussions MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
12. Closed match COVID-19 pandemic ⚫COVID-19 pandemic ⚫Suspension: from March 2020 ⚫France: Ligue 1 was cancelled in April ⚫England, Germany, Italy, and Spain: Resumed by late June and finished by early August ⚫Resumed matches were “closed.” ⚫“Closed match”=match without spectators MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
13. Closed match COVID-19 pandemic ⚫COVID-19 pandemic ⚫Suspension: from March 2020 ⚫France: Ligue 1 was cancelled in April ⚫England, Germany, Italy, and Spain: Resumed by late June and finished by early August ⚫Resumed matches were “closed.” ⚫“Closed match”=match without spectators MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Q: Is “crowd effect” vanished?
14. Closed match COVID-19 pandemic ⚫COVID-19 pandemic ⚫Suspension: from March 2020 ⚫France: Ligue 1 was cancelled in April ⚫England, Germany, Italy, and Spain: Resumed by late June and finished by early August ⚫Resumed matches were “unbalanced.” ⚫The leagues were already approximately two-thirds completed by the mid- March suspension. MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
15. Closed match COVID-19 pandemic ⚫COVID-19 pandemic ⚫Suspension: from March 2020 ⚫France: Ligue 1 was cancelled in April ⚫England, Germany, Italy, and Spain: Resumed by late June and finished by early August ⚫Resumed matches were “unbalanced.” ⚫The leagues were already approximately two-thirds completed by the mid- March suspension. MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Unbalanced schedule bias should be separetad from home advantage
16. Objective ⚫Analysis home advantage under COVID-19 pandemic ⚫Is the “crowd effect” vanished? ⚫Separate unbalanced schedule bias ⚫Outline of the analysis method ⚫Pairwise comparison ⚫Short-term rating method ⚫Compare the time series of the home advantage between normal and closed periods. MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
17. Closed matches under the COVID-19 pandemic ⚫Number of normal and closed matches ⚫“Closed” means “Without spectators” MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Country League Teams Matches (10/11-18/19) Matches Normal, 19/20 Matches Closed 19/20 England Premier League 20 3420 290 90 France Ligue 1 20 3420 279 0 Germany Bundesliga 18 2754 216 90 Italy Serie A 20 3420 240 140 Spain LaLiga 20 3420 270 110 Total 16434 1295 430
18. Basic stats ⚫2010-2020 ⚫Goals diff. per match ⚫Win prob. diff. MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
19. Basic stats ⚫2010-2020 ⚫2019/20 season ⚫Goals diff. per match ⚫Win prob. diff. MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
20. Basic stats ⚫2010-2020 ⚫2019/20 season ⚫Goals diff. per match ⚫Win prob. diff. ⚫In the closed period, the home advantages were reduced MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
21. Basic stats ⚫2010-2020 ⚫2019/20 season ⚫Goals diff. per match ⚫Win prob. diff. ⚫In the closed period, the home advantages were reduced ⚫“Home disadvantage” in Germany MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
22. Basic stats ⚫2010-2020 ⚫2019/20 season ⚫Goals diff. per match ⚫Win prob. diff. ⚫In the closed period, the home advantages were reduced ⚫“Home disadvantage” in Germany MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Unbalanced schedule bias should be separetad from home advantage
23. Outline ⚫Home advantage in football ⚫Closed match under COVID-19 pandemic ⚫Home advantage under COVID-19 pandemic ⚫Analysis method ⚫Results and discussions MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
24. Home advantage analysis: the method ⚫Logistic regression model ⚫Team i played at its home against team j ⚫The rating values are calculated so as to minimize σ 𝜖𝑖,𝑗 2 MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) 𝑠𝑖,𝑗 = ൗ 1 1 + exp − 𝑟𝑖 + 𝑟homeAdv,𝑘 − 𝑟 𝑗 − 𝜖𝑖,𝑗 𝑠𝑖,𝑗 = Τ (𝑠𝑖 + 1) 𝑠𝑖 + 𝑠𝑗 + 2 , 𝑠𝑖 : goals of team 𝑖 𝑟𝑖 : rating of team 𝑖 𝑟homeAdv,𝑘 : home advange of the league 𝑘
25. Home advantage analysis: the method ⚫Rating on scoring ratio ⚫Conversion to winning ratio ⚫𝐷𝑘 are calculated so as to minimize σ 𝜖𝑖,𝑗 2 MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) 𝑠𝑖,𝑗 = ൗ 1 1 + exp − 𝑟𝑖 + 𝑟homeAdv,𝑘 − 𝑟 𝑗 − 𝜖𝑖,𝑗 𝑟𝑖 : rating of team 𝑖 𝑟homeAdv : common home advange of the league 𝑤𝑖,𝑗 = ൗ 1 1 + exp −𝐷𝑘 𝑟𝑖 + 𝑟homeAdv,𝑘 − 𝑟 𝑗 − 𝜖𝑖,𝑗 = ෝ 𝑤𝑖,𝑗 − 𝜖𝑖,𝑗
26. Home advantage analysis: short-term estimation ⚫Proposed model: Estimate the rating of each team and the home advantage of the league simultaneously. ⚫Separate team strength from home advantage ⚫Useful under the unbalanced schedule ⚫Short-team estimation: follow the change of the home advantage ⚫Five matchweeks ⚫Classification of the periods: Normal, Mixed, and Closed ⚫Example: Premier league MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Matchweek 25 26 27 28 29 30 31 32 33 34 35 Spectator N N N N N C C C C C C Period N N N N N M M M M C C
27. Home advantage analysis: short-term estimation ⚫Proposed model: Estimate the rating of each team and the home advantage of the league simultaneously. ⚫Separate team strength from home advantage ⚫Useful under the unbalanced schedule ⚫Short-team estimation: follow the change of the home advantage ⚫Five matchweeks ⚫Classification of the periods: Normal, Mixed, and Closed ⚫Example: Premier league MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Matchweek 25 26 27 28 29 30 31 32 33 34 35 Spectator N N N N N C C C C C C Period N N N N N M M M M C C
28. Home advantage analysis: short-term estimation ⚫Proposed model: Estimate the rating of each team and the home advantage of the league simultaneously. ⚫Separate team strength from home advantage ⚫Useful under the unbalanced schedule ⚫Short-team estimation: follow the change of the home advantage ⚫Five matchweeks ⚫Classification of the periods: Normal, Mixed, and Closed ⚫Example: Premier league MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Matchweek 25 26 27 28 29 30 31 32 33 34 35 Spectator N N N N N C C C C C C Period N N N N N M M M M C C
29. Home advantage analysis: short-term estimation ⚫Proposed model: Estimate the rating of each team and the home advantage of the league simultaneously. ⚫Separate team strength from home advantage ⚫Useful under the unbalanced schedule ⚫Short-team estimation: follow the change of the home advantage ⚫Five matchweeks ⚫Classification of the periods: Normal, Mixed, and Closed ⚫Example: Premier league MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Matchweek 25 26 27 28 29 30 31 32 33 34 35 Spectator N N N N N C C C C C C Period N N N N N M M M M C C
30. Calculation example ⚫Fit result ⚫EPL. Matchweeks from 21 to 25 ⚫𝑟homeAdv is positive (red vertical dashed line) MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
31. Outline ⚫Home advantage in football ⚫Closed match under COVID-19 pandemic ⚫Home advantage under COVID-19 pandemic ⚫Analysis method ⚫Results and discussions MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
32. Main result ⚫Boxplot of distributions of 𝑟homeAdv ⚫Wilcoxon’s rank sum test ⚫Null hypothesis: The home advantage from two different categories were the samples from continuous distributions with equal medians. MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
33. Main result ⚫Boxplot of distributions of 𝑟homeAdv ⚫No significant difference between Past and Normal periods MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
34. Main result ⚫Boxplot of distributions of 𝑟homeAdv ⚫No significant difference between Past and Normal periods ⚫A significant difference between normal and closed periods ⚫Median in closed period is smaller than normal period MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
35. Main result ⚫Boxplot of distributions of 𝑟homeAdv ⚫No significant difference between Past and Normal periods ⚫A significant difference between normal and closed periods ⚫Median in closed period is smaller than normal period MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
36. Main result ⚫Boxplot of distributions of 𝑟homeAdv ⚫No significant difference between Past and Normal periods ⚫A significant difference between normal and closed periods ⚫Median in closed period is smaller than normal period MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Strong quantitative evidence of the impact of the crowd effect on home advantage
37. Analysis for each league: England Sample X Sample Y 𝑵𝑿 𝑵𝒀 p-value Past Normal 306 25 0.223 Past Closed 606 5 0.213 Normal Closed 25 5 0.578 ⚫The home advantage in the closed period has no significant difference from the past and the normal periods. MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
38. Analysis for each league: England Sample X Sample Y 𝑵𝑿 𝑵𝒀 p-value Past Normal 306 25 0.223 Past Closed 606 5 0.213 Normal Closed 25 5 0.578 ⚫The home advantage in the closed period has no significant difference from the past and the normal periods. ⚫However, GD in the closed period were reduced. ⚫Why? MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
39. Unbalanced schedule in England’s closed period ⚫ In the closed period, in England, weaker teams played more home games than stronger teams. MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
40. Unbalanced schedule in England ⚫ In the closed period, in England, weaker teams played more home games than stronger teams. ⚫Weak correlation (𝒓 ≃ 𝟎. 𝟒) between the final standings and the number of home matches in the closed period. ⚫No correlation in other leagues. Germany(0.2863), Italy(0.0867), and Spain(−0.1561). MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)
41. Estimated 𝑟homeAdv : England MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Sample X Sample Y 𝑵𝑿 𝑵𝒀 p-value Past Normal 306 25 0.223 Past Closed 306 5 0.213 Normal Closed 25 5 0.578
42. Estimated 𝑟homeAdv : Germany MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Sample X Sample Y 𝑵𝑿 𝑵𝒀 p-value Past Normal 270 20 0.163 Past Closed 270 6 <0.001 Normal Closed 20 6 <0.01
43. Estimated 𝑟homeAdv : Italy MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Sample X Sample Y 𝑵𝑿 𝑵𝒀 p-value Past Normal 306 20 0.029 Past Closed 306 10 0.065 Normal Closed 20 10 0.775
44. Estimated 𝑟homeAdv : Spain MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25) Sample X Sample Y 𝑵𝑿 𝑵𝒀 p-value Past Normal 306 23 0.020 Past Closed 306 7 <0.001 Normal Closed 23 7 <0.001
45. Summary ⚫The home advantage under COVID-19 pandemic was analyzed. ⚫Outline of the analysis method ⚫Pairwise comparison ⚫Short-term rating method ⚫Separate unbalanced schedule bias ⚫Compare the time series of the home advantage between normal and closed periods. ⚫Conclusion ⚫The home advantage was reduced in closed situation. ⚫Reduction amount was different between leagues. MATHSPORT INTERNATIONAL CONFERENCE 2021 (6/24-25)