The National Rugby League (NRL) competition provides an interesting example for an analysis of home team advantage as many of the Sydney teams in the NRL share stadiums. Recent research has found that there is a notable difference in the probability of a home team win depending upon the stadium and opponent type. This article discusses recent work conducted by Longden and Kannard (2014) that confirms that playing at a traditional Sydney stadium does provide an advantage to the home team even when team quality has been accounted for.
Keywords: Sports Economics, Home Team Advantage, Rugby League
JEL classification: C23
Suggested citation: Longden, Thomas, Home Team Advantage in the NRL (May 22, 2014). Review of Environment, Energy and Economics (Re3), http://dx.doi.org/10.7711/feemre3.2014.05.003
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Ever since the establishment of nine foundation clubs in 1908, the centre of rugby league in Australia has been based in Sydney. And while the sport has expanded to include teams from Queensland, Victoria and New Zealand, of the 16 teams in existence in 2012, 8 of them are located primarily in Sydney. Distances of travel between Sydney teams are minor, as reflected by the most distant stadiums [Note 1] being approximately 70 kilometres apart and a one hour drive without traffic. A range of teams share the same stadiums due to centrality to the city and guaranteed income from holding a match at certain stadiums.
Most Sydney teams tend to share stadiums but each does so with a different level of regularity. For example, in the period between 2001 and 2012, a grouping of seven of the Sydney teams played approximately 41% of their home games at a shared stadium, a grouping of six Sydney teams played approximately 87% of their home games at a traditional suburban ground, and a grouping of three Sydney teams played 81% of their home games at a shared stadium.
As a result the National Rugby League (NRL) competition provides an interesting example for an analysis of home team advantage and the focus on the NRL by Longden and Kannard (2014) is justified due to the peculiar nature of having multiple stadium types within the same city and team.
Between 2001 and 2012, 114 games were played at a shared Sydney stadium with the co-sharer. In these cases, the main difference for the competitors has been assumed to be control of marketing the game, control of where members or the team’s fans sit, whether the team uses the home or away change room with some auxiliary changes to the control of schedules or use of the field for training purposes. And yet, Longden and Kannard (2014) find that there is a notable difference in the probability of a home team win depending upon the stadium and opponent type. When a match is played at a shared Sydney stadium against a sharer the probability of a home team win for the period between 2001 and 2012 is found to be 50.83% in comparison to 44.10% for a match at a shared Sydney stadium against a non-sharer.
Analysing Home Team Advantage
Central to the analysis of Longden and Kannard (2014) is the use of probit regressions to calculate the probability of a home team win when the home team and the away team are of a similar quality. Similar quality is measured by the teams having had a similar amount of success in that season up until the point that the match commences. Success is measured in terms of competition points and the aggregated point difference from the matches during the season.
An interesting result in Longden and Kannard (2014) is that an unshared stadium and a match at a traditional Sydney stadium against a Sydney based rival were the most favourable home grounds during the 2001-2012 period. To clarify this for followers of the sport, these cases would be consistent with a match similar to: - the Brisbane Broncos playing at Suncorp Stadium against an opponent that was only better on the table by one competition point and one field goal (unshared stadium), and - the West Tigers versus the Manly Sea Eagles at Leichhardt Oval, if Manly were only better on the table by one competition point and one field goal (traditional Sydney stadium against a Sydney based rival). All probabilities in this article and in Longden and Kannard (2014) should be interpreted with an advantage of a draw and a field goal in favour of the away team.
In March 2014 a Sydney newspaper reported that once you exclude the Melbourne Storm in the period between 2007 and 2014, “the top three most successful home ground advantages all belong to suburban grounds - Manly at Brookvale (73%), Wests Tigers at Leichhardt (64%) and St George Illawarra at Jubilee (63%).” (Walshaw, 2014) However it should be noted that these figures are the home team win percentage and not the probability of a home team win. The probability of a home team win with teams of similar quality is an important factor as win percentages do not account for who the games are scheduled against. Irrespective of this, traditional Sydney stadiums tend to have probabilities higher than 50-50 and overall unshared stadiums are daunting locations to play, with a 2001-2012 average probability of 56.5%.
Probability of Home Team Win
Table 1, extracted from Longden and Kannard (2014), reviews the probabilities estimated for the most recent year reviewed, 2012, and the average for the period between 2001 and 2012. An interesting component of the research is the calculation of the probability of a home team win under the condition that the teams are almost evenly matched. This gives a different ranking of the most favourable stadium types than if you reviewed the raw home team win percentage. As shown in Table 1, the probability of home team win is deflated with respect to the home team win percentage. In addition, the order of the probabilities is different to the percentage of home team wins as accounting for key factors, such as team quality, notably impacts the ranking.
Table 1 - Comparison of the Probability and the Percentage of Home Team Wins
As an example, refer to the ranking (and appeal) of playing at a shared Sydney stadium against a team that shares the stadium. A probability of a home team win of 50.83% is estimated in comparison to the home team win percentage of 57.02% for a shared Sydney stadium with a sharer. A shared Sydney stadium against a non-sharer has been estimated to be the least favourable stadium across the period reviewed (2001 to 2012) with a probability of a home team win of 44.10%. Note that this slightly worse than playing at a marquee stadium (45.48%).
It should be noted that the most dramatic change over time has been that the probability of a home team win has substantially increased between 2001 and 2012 for the shared Sydney stadiums against a sharer. With the number of games classified as a shared Sydney stadium against a sharer changing over time, the pattern implies that teams have become more comfortable playing in such situations with a greater regularity of games, rather than notable increases in the occurrence of large crowds (with average crowds at these stadiums spiking in 2007 at almost 26 thousand per match).
The notable aspect of the analysis within Longden and Kannard (2014) is the estimation of an econometrically derived probability of a home team win within the National Rugby League (NRL) in Australia between 2001 and 2012. Econometric analysis makes an allowance for key factors, such as the difference in quality, and results in a ranking of the stadium types that are different to the home team win percentage that was realised during the period between 2001 and 2012.
Longden and Kannard (2014) confirm that a notable home ground advantage can be gained from different stadium types even after a consideration of the quality of the opponent has been made. The benefit of playing at certain stadiums has been speculated upon within the Australian media and the analysis of Longden and Kannard (2014) confirms that playing at a traditional Sydney stadium does provide an advantage to the home team. This advantage tends to be stronger against a rival team from within Sydney. Improvement in the probability of a home team win at a shared Sydney stadium against a sharer has occurred, but based on 2012 and the sample average it is still more advantageous to play such teams in a traditional Sydney stadium.
[Note 1] In this case, Brookvale Oval and Campbelltown Sports Stadium have been used as examples.
Longden, T. and Kannard, G. (2014) "Rugby League in Australia between 2001 and 2012: an analysis of home advantage and salary cap violations", FEEM Nota di Lavoro 53.2014.
Walshaw, N. (2014) "Brookvale Oval is one of the last sports venues where home ground advantage still exists", The Daily Telegraph, 7 March 2014. Accessed on 21 March 2014.
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