Historical Home-field Advantage

Home-field advantage is real. I don't really understand it myself - that is, I don't see an obvious reason for there being a home-field advantage. Does the home team benefit from playing on familiar ground? Fields aren't really that unique, are they? Besides, shouldn't there be a decrease in home-field advantage as time goes on and stadiums have been in the league for a while? Does the crowd tip a game in their team's favor? I have a hard time believing this as well. After all, these are professional athletes who do the same thing 162 days a year. I can't help but think about the Simpsons when Lisa chants "D-A-R-R-Y-L . . . D-A-R-R-Y-L . . . " as a single tear rolls down Strawberry's cheak - funny, but probably inaccurate. Also, aside from late innings in close games, the crowd usually doesn't react until after something has happened. Do players put in extra effort so they can get that gratification or are they doing their job like everyone else and a crowd roar is just an exciting bonus? Does travel cause additional fatigue in the visiting team or does a good nights sleep at home help the home team? Again, with 162 games a year, and with the home-team having to travel from somewhere else as well, I'd imagine baseball players becoming professional travellers and fairly used to road life.

Anyway, whatever home-field advantage is, it is important. As you can see from the plot below, the magnitude of home-field advantage has been pretty consistent over the last 105 years with the mean being at 19. Sometimes home-field advantage is greater than 19, sometimes it is less than 19. In statistics we expect this kind of 'noise' or 'variability', however, it is important not to see each individual value as representing changes in home-field advantage as opposed to the overall trend. The power score of 19 means that the home-team is expected to win approximately 55% of the time. If home-field advantage were a team, it would have comparable ability as the Texas Rangers. Competative, but it would be very unlikely to win the World Series - sorry JB.


Historical Home-Field Advantage