The NBA Title Race Has Not Been This Wide Open Since 2008-2009

This NBA offseason has been, for lack of a better adjective, crazy.  Anthony Davis was finally traded to the Lakers for a boatload of picks and young players (I had some thoughts after it happened). Kevin Durant and Kyrie Irving signed with a team which, just a few years ago, was described as one of the bleakest destinations in the NBA.  The Warriors, firmly ensconced as NBA royalty for so long, were suddenly in shambles.  Kawhi Leonard, the reigning finals MVP, was seriously considering joining the Lakers’ super team.  Except then he was actually 99% likely to stay in Toronto. But wait, actually he was going to the Clippers all along and taking fellow star Paul George with him!

All this turbulence and meteoric shifting of the NBA landscape got me thinking: who is actually going to win the whole thing?  This NBA season appears to feature the most wide open title chase that we have seen in years, and that’s the way Vegas sees it too.

Using historical title odds from previous seasons saved on sportsodds.com, and this year’s title odds from BetOnline (documented by OddsShark on July 9th), I plotted the title odds of the preseason title favorite for each season.  Here’s how the Los Angeles Clippers, the current favorite with a 25% implied championship probability (if the betting market were fair), stack up with their fellow title front-runners since the 2005-2006 season:

Screen Shot 2019-07-11 at 10.44.33 PM

We can see that the Warriors stranglehold on the NBA has dissipated.  The 2014-2015 and 2015-2016 seasons were more like this one by this metric, with the LeBron-led Cleveland Cavaliers installed as slightly more than a 25% favorite each year.  We actually have to go all the way back to the 2008-2009 NBA season to see a Vegas title favorite viewed as weakly as this year’s Clippers.  That season the Los Angeles Lakers were given a 22% chance to win a championship. They came through, however, defeating the Orlando Magic in 5 games.

But there is more to how open the title race is than just than just the strength of the favorite, so I decided to also look at something called information entropy.  Basically, the entropy of a probability distribution (such as the distribution of title odds) is a measure of its randomness.  The maximum entropy of a distribution with 2 outcomes, i.e. the flipping of a coin, is when each outcome is equally likely.  So you can think of more entropy  meaning more uncertainty in the championship race.  As an aside, I scaled the probabilities so that they summed to 1 for each season before doing the calculation.

Screen Shot 2019-07-11 at 10.43.50 PM

By this measure too, the NBA title race is uncertain as it has been since 2008-2009.

Finally, I think it is fitting that in such a topsy-turvy year, the three teams with the best title odds are not the same favorites as those of the previous few seasons.  The Clippers, Lakers, and Bucks have waited a long time to be taken this seriously, particularly the Clippers and Bucks.  Let’s hope that the pursuit of the suddenly very winnable 2019-2020 title is a blast!

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