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Home field advantage in the playoffs

Posted by Doug on January 3, 2007

Quantifying home field advantage in a particular league can be pretty tricky. Quantifying home field advantage in the postseason is even trickier, at least in the NFL, because the home team is almost always the better team. Since the merger the home team is 214-96 in playoff games, a decisive 69% winning percentage. (I am, of course, only counting the games where there really was a home team. That is, Super Bowls have been excluded.) But how much of that advantage is due to the home field and how much of it is due to the presumably superior quality of the team on that home field?

Prior to the 2002 NFC Championship Game, in which the visiting Tampa Bay Bucs beat the Eagles, I ran some numbers and discovered that in playoff games where the two teams had the same record, the home team enjoyed almost no advantage at all. Since the merger, home teams are just 32-28 in such games. But if the home team has a better record, the advantage seems to magnify very quickly. Here is a chart showing the records of home teams in playoff games against teams whose records were N games worse. For instance, the "1" line indicates that when the home team has a record that is one game better than the road team, the home team is 67-38.


-3 0- 1 0.000
-2 3- 3 0.500
-1 5- 3 0.625
0 32-28 0.533
1 67-38 0.638
2 51-14 0.785
3 29- 4 0.879
4 17- 4 0.810
5 8- 1 0.889
6 2- 0 1.000

Here is the same chart, showing only games since 1993:


-2 1- 1 0.500
-1 2- 1 0.667
0 9-10 0.474
1 33-18 0.647
2 29- 5 0.853
3 10- 2 0.833
4 3- 2 0.600
5 3- 0 1.000
6 1- 0 1.000

The pattern is the same: home teams are only about a 50/50 bet if the teams have the same record or if the home team has a worse record, home teams win about 65% of the time if they are one game better than the visitor, and home teams two or more games better almost never lose (46-9 since 1993). I would have expected the data to be a little smoother than that, maybe 56%, 62%, and 73% or something like that.

Let's compare these numbers to the regular season. I'll look at weeks 13 and 14; that's early enough that almost all teams still have something to play for, but late enough that the at-the-time records have a similar meaning to the records of playoff teams. Here are the results, first for all games since 1970 (compare this table to the first one at the top of the post):


0 60-47 0.561
1 62-35 0.639
2 54-33 0.621
3 44-15 0.746
4 38- 8 0.826

Now for only the games since 1993 (compare this table to the second one):


0 28-25 0.528
1 28-14 0.667
2 26-15 0.634
3 20- 7 0.741
4 20- 3 0.870

The big difference is with teams that have a 2-or-more-game advantage in the records. Based on these data, it appears that the home field doesn't necessarily confer an advantage in the playoffs. Instead, it magnifies whatever advantage is already there. Is this a statistical fluke, or is there something real here? Any theories?

This entry was posted on Wednesday, January 3rd, 2007 at 5:05 am and is filed under History, Home Field Advantage. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.