Posted by Andy on October 9, 2009
I got curious about how big the edge is for post-season teams playing at home. This is actually pretty easy to research with the PI.
In post-season history through 2008, home teams have won 668 playoff games. I found that by doing a Pitching Game Finder search, limiting to playoff games, limiting to home team, and limiting to wins. At the bottom of the results page is the total number of such games. Doing the same for losses shows 560 such games. So there you have it--home teams in the playoffs are 668-560, which is a winning percentage of .548.
Let's compare that to the regular season. The PI covers only 1954 to present, and through 2008 the home team has won 58,958 games. Meanwhile they have lost 50,335. (I got these numbers also with Pitching Game Finders, just going on regular season games instead of post-season.) That's a winning percentage of .539.
So in the playoffs, historically, the home team has had a slightly bigger edge than they have during the regular season.
In the wild card era (1995 up to games through 2008) home teams in the playoffs are 243-207, a .540 winning percentage. In the regular season over that same span, home teams are 17,918-15,343, a .539 winning percentage.
It seems that the extra edge home teams once enjoyed in the post-season has been eradicated in the wild card era. It's interesting to wonder why this is the case.
Historically, the schedule was more balanced meaning that all teams played a similar schedule. That's different today, where teams play many more games within their own division, meaning that more balanced divisions tend to see more even records (think about the NL Central in recent years) whereas divisions with a couple of crummy teams tend to produce teams with lots of wins (think about the AL East, where bad Baltimore and, until recently, Tampa Bay teams allowed the Yankees and Red Sox to rack up great records.) This means that in the past, teams with a better record probably really were better, whereas these days the unbalanced scheule means a 95-win team may not be as good as an 85-win team.
So historically in the playoffs the teams with home-field advantage tended to be truly better teams whereas these days it's a little more random.