Posted by Neil Paine on January 17, 2011
BBR reader Prashant wrote in with a good question yesterday:
"I just read John Hollinger’s article about the sustained success of the Spurs and Mavs and was wondering if there was any way to calculate the average deviation of a given team’s record over time? Basically, which teams are the most consistently good/bad/average over a set timeframe, say a decade? I would imagine the Spurs/Mavs/Clippers are atop that list, while the Celtics and Heat probably have a pretty wild deviation (from lottery team to title contender)."
Sure, the easiest way to look at this is to calculate the standard deviation of each franchise's year-to-year winning percentages over the given timeframe.
Of course, if we're going to include 2011 in the sample, we also need to make sure this year's records follow the same distribution as full-season records from the past. To do this, we regress every team's 2011 record to the mean by adding 4.5 games of .500 ball to their current record (40 games into the season, 4.5 is the amount of .500 games required to minimize the error between regressed wpct and end-of-season wpct):
|Golden State Warriors||16||23||0.410||0.420|
|Los Angeles Clippers||14||25||0.359||0.374|
|Los Angeles Lakers||30||12||0.714||0.694|
|New Jersey Nets||10||30||0.250||0.275|
|New Orleans Hornets||25||16||0.610||0.599|
|New York Knickerbockers||22||17||0.564||0.557|
|Oklahoma City Thunder||27||13||0.675||0.657|
|Portland Trail Blazers||21||20||0.512||0.511|
|San Antonio Spurs||35||6||0.854||0.819|
Once we've regressed 2011 to the mean, we can simply look at the standard deviation of each team's yearly winning percentages:
|1||San Antonio Spurs||0.710||0.057|
|5||New York Knicks||0.396||0.085|
|7||Golden State Warriors||0.419||0.095|
|8||Charlotte Bobcats (7 years)||0.386||0.098|
|11||Los Angeles Clippers||0.390||0.105|
|13||Los Angeles Lakers||0.635||0.113|
|16||Portland Trail Blazers||0.496||0.133|
|25||New Jersey Nets||0.467||0.157|
Prashant's intuition was spot-on; the Spurs and Mavs were indeed the two most consistent teams, while the Heat and Celtics were among the highest-variance teams of the last 10 years.
It was the Cavs, however, who truly stood above everyone in terms of wild talent fluctuations:
This particular period of time saw Cleveland bottom out with the collapse of the Ricky Davis era, draft LeBron James, climb to respectability, dominate the '09 & '10 regular seasons, and then fall apart again after James' departure. It's really amazing how they've literally run the entire gamut as a franchise in just 10 years.