Wednesday, May 21, 2014

Homecourt Advantage in the Playoffs

I've tackled homecourt advantage before as a topic, specifically looking at travel distance and rest. An interesting discovery, and one that's not too surprising after the fact, is that true homecourt advantage is smaller than most assume it is because more away teams play on the end of a back-to-back. The typical value people use is +3.2 for the home team, while if you take back-to-back games into account it drops to +2.8. That may not seem like much, but in the competitive NBA (and in the betting market) those margins are important.

One would assume then that the playoffs would actually have a smaller homecourt advantage than the regular season because there are no back-to-back games. Crowds may seem louder in the playoffs, but the NBA statistics world is one of skepticism -- we're not prone to giving credit for good will and exuberance. However, home teams are vastly better in the playoffs, and it's fairly consistent season after season.

Regular season
Regular season (no back-to-back’s)
Homecourt advantage (points per game)
Seasons 2000 to 2013

(Technical note: you can't simply compare the points scored by home teams in the playoffs to the away teams because teams don't always play an even amount of games. The better teams are most likely to play more games on their own floor. To correct for this, I added a "virtual game" to every series with an uneven amount of games. The virtual game is just an average of the real games played at one location. For example, for the Spurs-Blazers series, the virtual game is the average of games 3 and 4, so that now there are three games at San Antonio and three at Portland.)

As a check, a team rating system was built via linear regression for seasons 2010 through 2013 with the playoffs included. Homecourt advantage was estimated at 2.89, while in the playoffs it worth over an additional point at 4.02 overall. Over the same period using the simple method as in the above table, homecourt advantage was 3.94.

How did this season rate on its own? So far homecourt advantage has been roughly a full point less in the playoffs than the regular season at around 1.8. That's the worst differential by far since 2000 -- and given the crazy first round, it's not surprising. No season compares to this one yet, but there was another outlier season but in the other direction. In 2008, home teams were better by an average of 8 points. That's an enormous advantage; it's like the difference between a 42 win team and a 62 win team.

Crazy fluctuations notwithstanding, over multiple seasons homecourt advantage appears to be much higher in the playoffs than the regular season. There is something to play for. And if there's a winner in all this, it might be the fans for providing their home team the support when every game matters.


  1. Replies
    1. Look at the comment from Mike here

      Looks like there are more factors than just fouls or other subjective calls here.

  2. hello sir will you be computing rapm npi and rapm rpi for any further seasons after 2000 soon? thank you