The Diff: Regression to the mean and the Cavaliers

The Diff

For my entire archive of The Diff at WFNY, check out this tag. Last week’s edition tackled an aggregate of 60 mock drafts from around the Internet, which obviously didn’t prove that fruitful when the Browns took Barkevious Mingo (projected by only 3 mock drafts). Oh well.

The Diff

Back in my second-ever version of The Diff, on Jan. 23, I wrote over 3,000 words on six specific franchise comparisons for the current iteration of the Cleveland Cavaliers. Obviously, much has been written here at WFNY and elsewhere since about the hopeful trajectory of the Cavs organization, especially with the re-addition of head coach Mike Brown. Today, I’ll hope to share even more analytics behind previous NBA rebuilds and some statistics behind their variability.

 

Background knowledge

Through the 2011-12 NBA season, there had been 259 franchise-seasons with a .370 winning percentage or worse. This count begins with the 1961-62 season and only includes the NBA. The goal was to capture all 30-win-or-less-per-82-game seasons in the sport’s history and then analyze their eventual six-year winning pattern.

Here’s a quick table on these 259 such seasons:

Decade Seasons     *Wins Seasons
1961-1970 18 29.0-30.0 50
1970-1980 36 27.0-28.9 37
1980-1990 54 25.0-26.9 36
1990-2000 71 23.0-24.9 37
2000-2010 65 19.0-22.9 53
2010-2012 15 8.7-18.9 46
Total 259     Total 259

 

*Wins — Important caveat: Obviously, because of the 50-game 1998-99 season and the 66-game 2011-12 season, along with several other random 80- or 81-game samples in this historical outlook, everything in this study has to be standardized to an 82-game consistent pace. That makes it easiest to organize and makes sure that the averages are fair.

So that table above should make some logical sense. The distribution of wins, as you can kind of tell from that chart, practically follows a bell curve. There are as many bunched-together seasons of 29.0-30.0 wins as there are of 8.7-18.9 wins. Makes sense. Also, over time, with more teams joining the association (there were only 9 NBA teams in 1961-62, compared to 30 since 2004-05), more teams are going to have bad seasons. All seems to make sense and a necessary background to cover.

 

MLB regression to the mean

Back on March 3 in The Diff, I looked at the 124 MLB seasons with less than a 70-win pace between 1985-2010. Obviously, this research was done because of the Indians 69-win season a year ago and hoping to establish a historical norm for improvement. The results were fascinating, albeit later understandable.

“So, on average, these 124 seasons had 64.3 win-paces. The next year? A jump all the way up to 73.3 wins, on average, per the same 162-game schedule. So yes, on average, a team with less than 70 wins per 162 games has then improved by 9 wins per 162 games the next season.

That’s expected regression to the mean. There were certainly some outliers. And looking back at the table, the win improvements were most significant among teams with less than 67 wins per 162 games. But the point is clear: Because there are so many teams in professional sport leagues, and on average everyone has to finish .500 in total, then eventually bad teams will get better. It happens. The same phenomenon similarly occurs in the NBA, per my research.

 

The overall results

Just like in baseball, broken down by the splits of per-82-game season wins as I shared above, let’s go to the historical data to see how those teams improved the next year:

*Wins Seasons Y1 Y2 DIFF
29.0-30.0 50 29.6 32.9 +3.2
27.0-28.9 37 27.6 34.5 +6.9
25.0-26.9 36 25.7 32.1 +6.4
23.0-24.9 37 23.6 31.6 +8.0
19.0-22.9 53 20.8 28.6 +7.8
8.7-18.9 46 15.3 25.8 +10.5
Total 259 23.6 30.7 +7.1

 

Click here to view a locked Google spreadsheet of all 259 such teams.

There’s your synopsis in a nutshell: On average, an NBA team with 30 wins or less per 82 games has then improved by about 7 wins per 82 games the next season. Percentage-wise, that’s obviously a larger increase than the MLB splits I shared earlier. A similar pattern occurs, as expected, with the 8.7-18.9 win teams experiencing a larger jump than the 29.0-30.0 win teams.

At first glance, those year-over-year numbers are encouraging it would seem. On average, any bad team would take a 7-win improvement each season. That’s what has occurred historically. Now, what exactly does that mean for the Cleveland Cavaliers following the 2012-13 season and their current rebuild?

 

Current Cavaliers in context

Immediately following the summer 2010 departure of LeBron James, the Cavs posted 19-63 (.232) record. In the lockout-shortened 2011-12 season, they followed up with a much-improved 21-45 (.318) season. Then, battling injuries and in the final year of the Byron Scott era — marred by a near-historic failure in second halves — the Cavs slightly regressed to a 24-58 (.293) finish.

So there’s the record-by-record year-over-year narrative of this current iteration of the Cavaliers. Obviously, they’ve been a bit below-average overall when again it’s considered that sub-31-win teams have a 7.1-win improvement on average the next season.

The Cavs had an adjusted 7.1-win improvement — right on the mark — after the first season, but then regressed to the tune of an adjusted 2.1-win drop this past year. On the surface, that certainly would seem discouraging.

Comparing to the 259 seasons shared above, the 7.1-win improvement in year two ranked in the 53rd percentile. Perfectly average. Then, the 2.1-win decrease from year two to year three ranks in the 18th percentile among this group of seasons.

Comparing to the 251 seasons through 2010-11, this two-year per-82-game improvement of just 5.0 wins ranks in the 32nd percentile. On average, these 251 teams improved by 11.0 wins total from year one to year three. So now, let’s move on to some statistically similar franchise trajectories.

 

Three more franchise models

Most people love talking about the Oklahoma City franchise model. I included them in my six specific franchise comparisons last time in The Diff. But to add to the overall narrative and for more realistic models, here are three other franchise comparisons that intrigued me from this research.

Early ’80s Cleveland Cavaliers
81-82: 15-67
82-83: 23-59
83-84: 28-54
84-85: 36-46
85-86: 29-53
86-87: 31-51

Last time, I wrote about the trajectories of the pre-LeBron Cavs and the post-LeBron Cavs. Yet, these ’80s Cavs actually might be a better example. Their six-year trajectory was the most average of all of the teams in this sample. They improved by 8 wins, 5 wins, 8 wins, -7 wins and then 2 wins. Overall, it was a 16-win increase in six seasons.

After that ’86-’87 season, the Cavs then made the playoffs in nine of the next 11 seasons. They only advanced past the first round in two of those seasons. They were relatively mediocre in the big picture of NBA history, but their overall ascent into relevance was very close to expected historical averages.

Early ’90s Minnesota Timberwolves
91-92: 15-67
92-93: 19-63
93-94: 20-62
94-95: 21-61
95-96: 26-56
96-97: 40-42

The reason why I first caught onto this comparison: The ‘Wolves had a similar 5-win improvement from year one to year three in this span. Of course, Minnesota was an expansion franchise for the ’89-’90 season, so this six-year span actually was their only their third as an NBA team.

The biggest difference for Minnesota took place with the drafting of Kevin Garnett No. 1 overall in the 1995 draft. They struggled to make much traction before his arrival. Then, they improved by 14 wins in his second season and made the playoffs in eight of the next nine seasons. Similarly to the Cavs, they only advanced past the first round once. Garnett’s departure for Boston in July 2007 marked the start of another rebuild.

Mid ’00s Charlotte Bobcats
04-05: 18-64
05-06: 26-56
06-07: 33-49
07-08: 32-50
08-09: 35-47
09-10: 44-38

Poor Charlotte. While everyone would like to fixate on their 28-120 record in the last two seasons, they actually had a fairly standard six-year rise to mediocrity with the start of their franchise history in ’04-’05. They were thus two years faster than Minnesota’s pattern above beginning with their third year in existence.

The Bobcats only have made one playoffs in their nine years of existence and that was the final year of this stretch. Coached by Larry Brown, they were an up-and-coming team that folks thought would at least be in the lower-tier playoff conversation for the next half decade or more. Three members of the Stephen Jackson-Gerald Wallace-Raymond Felton-Boris Diaw were gone within 18 months however, sparking another rebuild for the Bobcats.

 

Final thoughts

The purpose of today’s post and this latest research was to add more statistics and more historical data to the conversation of the Cavaliers’ rebuild. The three new models above show another pattern that’s quite common when aggregating all of these bad seasons: Eventually, the team becomes at least mediocre.

The ’80s Cavaliers made the playoffs in nine of 11 seasons; the ’90s Timberwolves made the playoffs in eight of nine. Eventually, neither were good enough to even make the NBA Finals, but both were consistent playoff contenders year after year. Think of the modern day Atlanta Hawks or Memphis Grizzlies, for example.

While such a result is ultimately probably unsatisfactory for Cleveland fans and their WFNY mentality, it’s just simply what happens most often in a rebuild. Eventually, by year six, the team has reverted to very average numbers close to a 41-41 win season. That’s very simple regression to the mean and at worst, it should happen in due time for this current iteration of the Cavs.

So next year? 2013-14? Year one of the second Mike Brown era? For now, a safe bet would be a 7-win increase, per the usual improvement of these 259 teams overall and of 24-win teams specifically. Obviously, the hope is to start competing for the No. 8 spot in the playoffs. But for now, about 30-32 wins is the historical expectation of what’s up next for Cavalier fans. From there, we’ll see about the eventual ceiling.

  • BenRM

    WFMY (Waiting for Mediocre Years)

  • The_Real_Shamrock

    WFND (Waiting for Next Decade)

  • mgbode

    “simply what happens most often in a rebuild”

    it’s all great research Jacob, but in the NBA where only a few teams really end up being good enough to win a championship, it should be fully expected that most rebuilds end up with decent but not championship caliber squads.

    even the OKC example (where Presti hit on a ridiculous number of trades and draft picks) has yet to win a championship (and w/o Westbrook, it’ll be tough to imagine them doing it this year).

    that’s okay. i’m going to still hold out hope that we are the exception, the outlier.

  • JacobWFNY

    “it should be fully expected”

    Again, that expectation has to be repeated every now and then. That’s all I hoped to set out to do.

    Your logic is obviously right; only 1/30 teams win a title every year and out of those 30 teams, only 4-6 really are true contenders.

    But in Cleveland, you never know what fans might think.

  • mgbode

    yes, I definitely agree that it bears repeating.

  • http://twitter.com/laughingcavs Laughing Cavs

    Very nice to see this concept hashed out in an article.