Sunday, July 05, 2009

Which sport has the best home field advantage?

It's been known for many years now that the home field can provide a significant advantage toward a win in sports. What I didn't realize till recently is how much the home field advantage varies relative to different sports.

According to Dr. Ray Stefani of California State University, there are three possible contributing factors to the home field advantage:

1) The visiting teams travel fatigue. (physiological factor).
2) Effect of the home crowd on the home and visiting team by cheering or sneering as the case may be. (psychological factors)
3) The home teams familiarity of the home venue (tactical factor).

Dr. Stefani wrote Chapter 12 of Statistical Thinking in Sports, by Jim Albert and Ruud H. Koning, entitled Measurement and interpretation of home advantage. Using data over multiple seasons of Rugby Union, Soccer, NBA, Australian Rules Football, NFL, College Football, NHL and MLB, Dr. Stefani presents the following pecking order for Home field advantage. Where home field advantage is defined as a fraction or percentage of (home wins - home losses)/total games.

  • Rugby Union ---------- 25.1%
  • Soccer ----------------- 21.7%
  • NBA -------------------- 21.0%
  • Australian Rules FB -- 18.8%
  • NFL ---------------------17.5%
  • College Football ------ 16.6%
  • NHL -------------------- 9.7%
  • MLB ---------------------7.5%
Dr. Stefani explains these statistics with several additional factors aimed at describing the fatigue factor.

  • Number of players per team in play.
  • Playing time in minutes (actual time ball or puck is in play)
  • Overall Game length in minutes
  • % IP
  • Max number of substitutions
  • Can a substitute player reenter the game.
In his conclusion the physiological factor seems to be the easiest of the three factors to assess and model. Clearly rugby, soccer, and the NBA have a high degree of physical demand and long periods of continuous play. MLB on the other hand although the average game length is 165 minutes only really has about 24 minutes of significant play. Hockey which seems like it would have a high fatigue rate has comparable game action with the NBA but fatigue is reduced to an average number of 4 lines changed every 45 seconds to maintain the high pace. Therefore from a fatigue standpoint there are some good reasons why MLB and NHL show up last on the list.

I didn't spend additional time trying to analyze the dataset that can be found online. Dr. Stefani did an excellent job presenting the data and conclusions about his research.

What intrigues me are the questions that still could be answered with further research:

How do you quantify the psychological effect of the home crowd? How can you evaluate how the venue plays a role? Obviously in baseball venues probably have the most disparity in playing field. Differences in actual field dimensions are evident. Some baseball statisticians have determined park factors for each major league ballpark comparing runs on the road vs runs at home. So these park factors may have an influence in the outcome of the home field evaluation in baseball, but most other sports use a very similar playing surface.
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