Freelance Friday: Parity in the NBA Over Time
By Guest Post
Freelance Friday is a semi-regular series at The Nylon Calculus where we invite submissions from readers and practitioners in the hope of making basketball analytics more democratic and inclusive. Submissions, questions and comments can be directed to TheNylonCalculus at gmail dot com.
Today’s submission is from Patrick Oxford and concerns the evolution of parity in the NBA from the pre-three point era until present day.
There is a lot of discussion about how much parity exists in the NBA and how it compares to the past, so I decided to look at just how much parity has changed in the NBA over the years. First off let’s define parity as the evenness between teams in any given season. I looked at Dean Oliver’s Four Factors of Basketball Success along with my own Four Factors Rating (FFR) which is a linear regression of the 8 components of the Four Factors of Basketball Success[2. Details of the FFR regression include
]. A lower standard deviation in FFR means more parity, while a greater standard deviation means bigger disparities between best and worst teams and thus less parity.[1. I looked at every since 1974 because that was the first season where the Four Factors were recorded.]
The table above shows the parity score for every post-74 season in the NBA. In that time, there have been five main eras that have seen certain changes in parity. The 1974-79 era is referred to as “Pre-3pt” as all of it’s years fall before the league added the 3-pt line. 1980-90 era is referred to as “Pre-Jordan, and is characterized by strong offenses that correlated with the parity of this era. 1991-98 is the “Jordan era”, named after his Airness, 1999-2007 is known as “Post-Jordan”, where the increase in parity immediately following Jordan’s 2nd retirement is apparent. Finally 2008-2015 is called the “3pt era which becomes more and more of a fitting name with each passing season if trends continue.
Pre-3pt:
This period saw the most amount of parity, with only 1 season over 3 standard deviations for FFR in 1974. The extreme balance in 1976[3. 1.922 standard deviations .] may have been the last push needed to convince the owners that taking over the talent from the ABA was a must. The average FFR standard deviation was 2.738, lowest of all the eras, showing how flat the level of talent was across the league. The NBA lacked many of the stars it had the previous decade like Bill Russell, Wilt Chamberlain, and Jerry West and the new stars weren’t as strong outside of Kareem Abdul-Jabbar who had less success at a team level as the era progressed. Once the players were acquired from the ABA it certainly helped as Julius Erving, Moses Malone and others made an impact on the league.
The least balanced year of this period was 1974, largely due to the strength of Kareem and his strong supporting cast in Milwaukee. That team posted the highest FFR of the era at +6.995in the last year of the Kareem-Oscar duo. 1976-77 saw the most parity of any season in this study. The bad teams just weren’t very bad. The Bulls at -2.55 FFR have the distinction of being the most competitive any worst team in any given season study. Of course, another word for parity is “mediocrity,” and this was a low point for the league in terms of talent. The influx of ABA players for the next season were just what the league needed to solve the talent shortage, evident in the jump in the FFR standard deviation.
Pre-Jordan:
In this era the league was still relatively balanced. The average FFR standard deviation was 4.267, and the highest rated team by FFR in the era was the 1987 Lakers at +9. The Lakers and Celtics dominated the era with the 76ers grabbing the championship in 1983 and the Pistons ending the era with two straight. The lack of dominant regular season teams compared to more recent eras may have been caused by fewer teams putting weight into regular season performance or more teams being competitive on a nightly basis. The league was still small enough that it was difficult to not make the playoffs, while the talent level was not diluted by expansion.
1984 had the most parity in the “Pre-Jordan” era. The Celtics posted a season best +6 FFR, but that was the second lowest “season best” FFR of this era behind the Celtics in 1988. The bottom of the league was competitive with the lowest FFR belonging to the Bulls at -4.49, which is the second most competitive worst team behind the aforementioned 1976 Bulls. The drop in FFR standard deviation from 1983 to 1984 looks large, but the 1983 Houston Rockets are a large part of that posting a -11.76 FFR. This was the worst single season by any team up to this point in the study, and would remain so until 1993.
1989 was the first year that there were 3 really bad teams. Coincidentally, this was the first year of expansion with the (original) Charlotte Hornets and Miami Heat joining the league. Along with those two, the Clippers joined those squads in the basement all with FFR ratings of -8.37 or lower. Four strong teams[4. the Cavaliers, Lakers, Suns, and Pistons, +8.79, +7.15, +6.82, and +6.5 FFR respectively.] led the pack. The wide separation between the top 4 and the bottom 3 severely decreased parity. Sixty percent (15 of 25) teams had a positive FFR, indicating that the majority of teams were trying to compete, but 6 teams finishing at worse than a -5 FFR was the primary reason for this year having the lowest parity of the era.
Jordan Era:
This was the most unbalanced period of the post-1974 era. The trend of decreasing parity continued from the previous era with an average FFR standard deviation of 5.51. As expansion continued, there were simply not yet enough NBA-caliber players waiting to fill the additional spots from the 6 teams added between 1988 and 1995. 1998 saw the least balance of any post-74 season, in that season, five teams finished with -8 FFR or lower, “led” by the Nuggets at -13.04.
1991 started out the era with the most parity it would see with a FFR standard deviation of 5.03, yet it still ranks as having the 12th lowest parity in this study. The Nuggets were the only really bad team at -9.5 while the Bulls and Trail Blazers were each strong at +9.93 and +8.83 respectively. The Bulls continued to build upon their success this season the following season with a +11.52, second highest in this study. The single least competitive team in the study is the Mavericks from 1993. At -16.15 FFR they are the primary reason for this year being less competitive than the prior year as Dalls was over 3 standard deviations below average.
The season with the least parity in the study in the entire study was 1998, and the strongest team during the regular season was the Lakers at +9.28 FFR. The Bulls may have won the title, but they didn’t experience the same regular season dominance they were accustomed to with Jordan playing, only posting a +6.99 FFR, not much more than 1 standard deviation above average. The bottom of the league was a disaster with 5 teams finishing below -8 FFR, the worst of which was the Nuggets at -13.04 FFR.
Post-Jordan:
There was a steep decline in FFR Standard Deviation starting in 1999, and a smoothing out as the era continued. A turn towards more parity was the trend in this era, as the league saw a period resembling the 80’s more than the 90’s in terms of balance. The league finally had enough NBA-caliber players to fill most rotation spots competently. At the same time teams had not yet learned the best ways to exploit the new defensive rules, leveling the playing field slightly
The 2000 season saw the least amount of parity in the Post-Jordan era, although not by much. The Lakers were the only dominant team at +9.23 FFR while both the Bulls and Clippers were terrible, posting FFR’s of -11.46 and -12.13 respectively, placing them as the two least competitive teams of the era. In 2006 the highest amount of parity for the era was experienced, and the primary reason was not having a dominant team. The highest rated team by FFR during this season was the defending champion Spurs at +7.65, lowest of the era among season highs. The bottom of the league only had 1 really bad team, the Trail Blazers, who finished with a -10.4 FFR.
3pt Era:
Our current era is mostly known for the prevalence of the 3-pt shot. Three attempts per game skyrocketed after the 2012 lockout season. To remain competitive, teams are having to become smarter with shot selection to maximize efficiency, increasing shots at the rim and 3-pt attempts and decreasing inefficient midrange shots. Interestingly, there appears to be a correlation between total 3-pt attempts per game and FFR Standard Deviation. As more teams are increasing their 3-pt attempts, the competitive advantage is diminished as more teams are subject to the nightly variance of making or missing shots. The Warriors were the lone elite team in 2015 with a +10.26 FFR, second highest since the 1997 Bulls, just behind the 2008 Celtics[2. Those 2008 Celtics dominated in the first year of their Big 3, and they were the most dominant non-Jordan Bulls team by FFR in this study at +10.84. That year also saw the least amount of parity since 1998. The Heat and Supersonics were at the bottom of the standings at -8.74 and -8.93 FFR respectively.]. With no other elite teams, and no teams that finished with worse than a -10 FFR (Knicks were close at -9.89), parity was at an era-high this past season.
The league seems to be trending towards more parity at the moment with the most recent season having the most parity in the era, and that is something that should be encouraged. 3-pt attempts will continue to rise, and as more of those mid-range shots are shifted to the rim, there will be more free throw attempts, resulting in more efficient offenses or a change in defenses to force more midrange shots. Three of the Four Factors are hovering near historical lows while Effective Field Goal % is at or near a historical high. Defenses are going to be forced to find alternatives to current schemes as this rise in 3pt shooting continues. Switching on defense is becoming more and more of a requirement as of late, and the ability to switch and guard multiple positions is going to be something that separates the good teams from the elite going forward. Anything else that can create a competitive advantage will be utilized by the forward thinking teams as the slower front offices begin to catch on and equalize the obvious competitive advantages.