FanPost

Competitive Balance In The Modern NBA

Jesse Johnson-USA TODAY Sports

Things are bad, Wolves fans. It seems like we've been terrible forever, and it looks like we'll be terrible some more. But what does our long streak of awfulness mean? Are we doomed to labor at the bottom of the rankings until the end of time? How much can we reasonably expect our team to improve from a statistical standpoint over the next few years, and how long do we have to languish in awfulness assuming we finish as one of the bottom five teams in the league.

Change In Regular Season Rank Over Seasons

On the whole, it's the most likely that a team will retain about the same ranking as they held the previous year in any given year. Ninety-five percent of the time, a team can expect to either improve or worsen their standings by about half a rank (equivalent to tying the team one rank above or below their own the previous year). But that's to be expected, since every team needs to go somewhere, and there will always be the same number of slots (or roughly the same, depending on expansion). A mean value isn't really informative for this kind of data.

Change In Rank Over One Season

So instead, how do these numbers compare to the amount of change that's expected by a given finishing position in the league? Thankfully, most teams do not tend to languish in the bottom five slots. Year to year, most teams at the bottom of the rankings can hope to increase their standings by around five places the following year. Likewise, the teams finishing at the top of the league can expect their record to decline by closer to five spots the following year. Roughly the bottom 15 teams can expect to improve their record, while the top 12 teams have a better chance of their record worsening.

Density Plot Of Expected Position Change Over One Season

We can do a little bit of eye-test-y stats here, too, using a density plot. We notice that there's a large cluster of teams that finish between first and tenth in the league, and that amongst these teams there's a tendency to fall back less than others. In the NBA it's good to be king, and while bottom teams do move up, mid-tier clubs have a tendency to languish in the lava lamp of rank 15-25 or so. And how have the Wolves done historically?

<a class='sbn-auto-link' href='http://www.sbnation.com/nba/teams/minnesota-timberwolves'>Timberwolves</a> Historic Change In NBA Position

Huh. Well that's something. ... Woof.

But hey! Maybe things are changing over time! Maybe the league is becoming more competitive as the top dogs find themselves at the bottom again. The Lakers have fallen low, and the Heat appear to be experiencing a steep decline. Maybe this is a sign that the league under the last CBA has made contracts and team affiliations more fluid, and it may be easier than before to reverse a losing trend.

In a 2007 paper, a method of analyzing the amount of fluidity in a league over time is outlined. Simply put, based on the average amount of league-wide "shuffle" in the standings year over year, it should be possible to quantify how fluid and therefor competitive a league is. This measure is called the "churn." If no team changes its position in the standings from one year to the next, churn is zero, and the league is effectively locked.

Churn In The NBA Over Time

So where are we in the NBA? From the NBA/ABA merger, churn has increased year over year. Teams appear to have more mobility over time, to the point that where teams once had the ability to change position by four slots a year, they now can expect to move around six slots. Great news for a bottomed out Wolves team, right!

League Expansion

Well... Not exactly. Y'see, there's this little thing called league expansion. As the league has grown over time, that means that the amount a team can jump in a given year doesn't have the same meaning. Moving two places in a 20 team league doesn't mean the same thing as moving two places in a 30 team league. Because of this, the group in the above paper introduced a measure called adjusted churn, which takes into account the changing number of teams in a league over time.

Adjusted Churn Over Time

Adjusted churn gives a value between zero and one, with zero representing a totally locked league and one representing a maximally fluid league. Applying this to the NBA data, we get the above. Not as pretty. If you squint hard enough you can maybe see an upward trend, but for the most part the league as a whole has been very steady in the amount teams shuffle the standings deck every year. Overall, we're closer to a locked league than a maximally fluid one, which means there are some limits on how big of a swing we can expect year over year.

Conference Adjusted Churn

We can also look at the individual conferences and see what level of mobility exists there. Interestingly we can see that the West has remained fairly locked, so the knock-down-drag-out level of toughness hasn't resulted in a conference that is anybody's guess, but has instead decreased its mobility. By comparison, the East has gone from a locked conference to a revolving door of standings changes. Teams in the Eastern Conference can reasonably expect a full additional change in rank for any given team over the previous season compared to the West.

So if all of this makes your stomach... well... churn, hope real hard that Seattle gets an expansion team and the Wolves end up in the East. Otherwise, we might be in for a bit of a long haul here. But there are outliers, too! As always, Wolves fans are stuck hoping that lady luck leaves something other than a flaming bag of wolf turds on the doorstep. But these things happen. Roughly 25% of the time, a team jumps more than four places in the standings the following year. And teams that finish in the bottom three in the league have a roughly 50% chance of improving at least five places in the standings.

Hey, if nothing else, it's proof it's hard to get any worse.

Note: Thanks to this blog entry at OUseful.info, which got me thinking about this metric.