|Again, X is number of teams, Y is standard deviation of winning percentage|
The Early Days - 1950s
The 50s were an interesting time for the NBA. The league was small, there was no three point line, and the shot clock didn't come to the league until the 1954-55 season. Moreover, the league - and the country - had not quite worked out a number of racial issues, and so the league was dominated by white players. What's more, because basketball was still new, there were not throngs of kids who grew up playing the game (football and especially baseball were the sports of the time in America), meaning it was harder to find talented athletes.
The 1952-53 season was one of the "least competitive" - at least by standard deviation of winning percentage - in the history of the NBA. With a SD of .198, the league was both top and bottom heavy. Interestingly, no team won more than 70% of their games, but the SD is so high because only one team won between 40 and 60% (the Fort Wayne Pistons). At the high end, the New York Knicks went 47-23, the Syracuse Nationals went 47-24, the Boston Celtics went 46-25, the Minneapolis Lakers (which makes much more sense than the Los Angeles Lakers) went 48-22, and the Rochester Royals went 44-26. On the other hand, the Baltimore Bullets and Philadelphia Warriors went 16-54 and 12-57 respectively.
Despite the disparity in winning percentages in 1952, point differentials were much smaller. The league's high-scorers from Rochester averaged 86.3, while the Indianapolis Olympians averaged 74.6 points per game. Both are astoundingly low by modern standards, but more remarkable is the gap - or lack thereof - between the two. Consider the 2009-2010 NBA, in which the Phoenix Suns averaged 110.2 ppg, while the New Jersey Nets put up only 92.4. As for point differential, the Milwaukee Hawks went 27-44, but were outscored, on average, only 77.4 to 75.9. One gets the sense that they fell behind, and then had the clock milked against them.
The shot clock changed everything in the NBA, and it's no accident that three of the most competitive season in NBA history were 1954-55, 1955-56, and 1956-57. Those were the first three seasons of the shot clock, and the clumping of W-L records alone shows that teams were really struggling to understand how to play in a transforming league. SDs for those years were .087, .061, and .054(!).
That the league was changing was obvious. In 1954-55 the Boston Celtics averaged over 100 points per game (on both defense and offense), both NBA firsts. No team stood out in those three seasons, however, despite the complete transformation of the game. In part this was due to a small league, in part a lack of standout talent, in part a shorter season, and in part, of course, a drastic rule change. It took until the 1957-58 season for some team to start to pull away from the pack, some team to start to "get it" in this new era of no-running-out-the-clock basketball. That team? The Boston Celtics. Not surprisingly, they had been the best offensive team in the league before the shot clock, and they continued to be for years afterwards. What catapulted them to dominance, however, was defense. They kept scoring, and added Bill Russell as a rookie in 1956-57. Even that year they won their first NBA championship and finished 44-28, but the league as a whole was still bunched together (the Western Division featured no less than three 34-38 teams).
As Russell's career took off, the competitiveness of the league disappeared. The Celtics became such a dominant force that by the 1959-60 season, the pendulum had swung so far in the other direction that a 59-16 Celtics team, combined with a 19-56 Cincinnati squad, led to a SD of .188, the second highest in league history. Of course, 1959 is one of those seasons where we have to wonder about what "competitiveness" really means. The uneven talent distribution did mean that Cincinnati, Minneapolis, New York, and Detroit got hammered far more often than not, but the other four teams were all about .600. Boston's 59-16 was countered by Philadelphia's 49-26, and Syracuse's 45-30. The St. Louis Hawks finished 46-29 in the West, as well.
By now scoring was way, way up as well. The Celtics, in 1959, averaged 124.5 on offense, and 116.2 on defense. Average! No wonder Wilt Chamberlain was able to put up 37.6 a game, or Bob Cousy averaged almost 10 assists. Anyway, this is one of those seasons, ironically, where "everyone had a good team" in the opinion of Bill Simmons, and he has a point. Everyone may not have had a good team, but four teams definitely did. Consider the following key players (win shares in parentheses):
Boston - Bill Russell (13.8), Bob Cousy (7.9), Bill Sharman (7.8), Tom Heinsohn (7.7)
Philadelphia - Wilt Chamberlain (17.0), Tom Gola (9.9), Paul Arizin (9.2)
Syracuse - Dolph Shayes (9.5), George Yardley (9.0), Larry Costello (8.0)
St. Louis - Cliff Hagan (11.8), Bob Pettit (11.5), Clyde Lovellette (9.0)
Who cares if Minneapolis's Elgin Baylor (11.5, with no support from anyone else on the team) was the only other really good player in the league, the best teams were all loaded with talent. Which, of course, only begs the question: which is better, a league with 4 great and 4 terrible teams, or a league with 8 teams who all have a change to beat each other?
The End of the ABA, and the Merger - 1970s
The early and mid 1970s were an interesting time for the NBA. The ABA - which included three-pointers and lots more slam dunks - emerged as a competitor, but also hemorrhaged money and was responsible for seasons that were, by any measure, extremely uncompetitive. It was, in short, more of a show league, but it put pressure on the NBA just the same. 1972 was a pivotal year, in particular, because the NBA switched TV partners, moving to CBS from ABC after the season. It was also, by standard deviation, the single least competitive season in NBA history.
On the plus side, a 68-14 Boston Celtics team romped through its division, while 60-22 Milwaukee and 60-22 Los Angeles led the way in the Western Conference. The New York Knicks ended up upsetting Boston in the Conference Finals and went on to crush Los Angeles in five games in the Finals. But, like 1959, 1972 was marked by a handful of great teams and a handful of truly awful ones.
On the minus side was Philadelphia, finishing an unheard of 9-73, a full 59 games behind Boston. Buffalo - from Philadelphia and Boston's division, went 21-61, meaning the Atlantic had two of the best and two of the worst teams in the NBA. Portland, cellar-dwellers in the West, was also an uninspiring 21-61, and their division mates, the Sonics, went 26-56. In all, it was a year of extremes, in a league waiting for a merger (which would bring, among others, Julius Erving to the NBA), with its TV deal caught in limbo, and yet with all of the attention that a third New York - Los Angeles finals brought to the league. Throw in Wilt Chamberlain and Kareem Abdul-Jabaar, and the NBA was making inroads in mainstream America.
Meanwhile, the ABA was falling apart. The 1974-75 and 1975-76 seasons were, well, horrible. With the merger looming, and teams facing bankruptcy, competitive balance suffered. Posting SDs of .191 and .190, the last two seasons of the ABA were more or less a joke. Already down to 10 teams in 1974, after a 27-57 season Memphis closed up shop, and San Diego and Utah both played fewer than 20 games in 1975, finishing 3-8 and 4-12 respectively before calling it quits. The final season of the ABA, then, featured only 7 teams including a Virginia squad that finished 15-69 for the second year in a row. Ultimately, in a top heavy league, it made sense for the New York Nets, the Denver Nuggets, the San Antonio Spurs, and the Indiana Pacers to make the jump to the NBA as the ABA finally closed its doors.
The 1975-76 NBA season had been, in stark contrast to the ABA, highly competitive (SD of .105). At 54-28, Boston led the Eastern Conference, while a 59-23 Golden State team led the West. Other than those two teams, however, no one finished higher than .600, while only one team - 24-58 Chicago - finished below .300. Parity was the word, and so the addition of four good teams from the ABA, along with a redistribution of talent from the folding ABA teams, meant that 1976-77 would be one of the most competitive ever in the NBA.
With a SD of .098, 1976-77 is the most competitive season since the merger. It's no accident that it happened the first year after the merger, for reasons discussed above. For the second straight season, only one NBA team finished below .300, the New York Nets. Meanwhile, the other ABA transfers did better, with San Antonio and Denver posting solid above .500 seasons (Denver, in fact, won their division), and Indiana finishing 36-46. No one really stood out in 1976, however, with the 53-29 Lakers the class of the league.
This was no diluted league, however, and while the lack of great teams might frustrate some, there was no shortage of great players. Take a look at some of the leader boards to see what I mean:
1) Pete Maravich - New Orleans
2) Kareem Abdul-Jabaar - Los Angeles
3) David Thompson - Denver
4) Billy Knight - Indiana
5) Elvin Hayes - Washington
1) Kareem - Los Angeles
2) Moses Malone - Houston
3) Artis Gillmore - Chicago
4) Elvin Hayes - Washington
5) Bill Walton - Portland
1) Kareem - Los Angeles
2) Gilmore - Chicago
3) Hayes - Washington
4) Dr. J - Philadelphia
5) Bobby Jones - Denver
Not even mentioned in those statistical categories are first team All-NBA-er Paul Westphal and 2nd teamers George Gervin, Geroge McGinnis, and Jo Jo White. Rookie of the Year Adrian Dantley, All-Stars Dan Issel, Bob Lanier, Rick Barry, Dave Cowens, John Havlicek, Bob McAdoo, Rudy Tomjanovich, and Earl Monroe are also worth mentioning. In short, it was a banner year, talent-wise, for the NBA. It just so happened that few of those players were teammates (Issel, Bobby Jones, and David Thompson with Denver were possibly the best trio in the league, but not good enough to get past Bill Walton's eventual champion Portland).
The NBA continued to see parity in 1977-78 (SD of .111) and 1978-79 (SD of .103), but eventually we settled into a happy medium as Larry Bird and Moses Malone came into their own in the early 80s, followed, of course, by MJ.
Modern Era - 1990s and Beyond
There's not as much to say about the NBA since the merger. As the three-point line became and accepted part of the game, and as free agency settled in and the draft became what it is today, changes to the league structure have become much smaller. As you can see in the graph, there's a much narrower range of variability from one season to another in the modern NBA, and that's probably a better measure of competitiveness than anything else. The modern NBA has struck a balance, for the most part, between too few and too many teams being in contention each season, with room for the occasional extreme.
A couple noteworthy seasons include 1983-84 and 2006-07 (with SDs of .115 and .132, respectively), which were both on the "competitive" end of our SD spectrum. 1983 was Bird's first MVP season, featuring a - guess who? - Los Angeles vs. Boston finals. While no team really pulled away, both Boston and Los Angeles were excellent, and the SD is so low mainly because no team was truly awful. The 27-55 Chicago Bulls, of course, were one of the league's worst, and bad enough to land none other than Michael Jordan in the draft the next season (at #3 overall).*
* This was a crazy, crazy draft. Check out some of the picks, here:
1) Hakeem Olajuwon - Houston
2) Greg Oden - Portland. Oops, I meant Sam Bowie. It's just, they're exactly the same player. And, just like with Kevin Durant, the next guy was maybe a little better.
3) Michael Jordan - Chicago
4) Sam Perkins - Dallas
5) Charles Barkley - Philadelphia
7) Alvin Robertson - San Antonio
9) Otis Thorpe - Kansas City
11) Kevin Willis - Atlanta
16) John Stockton - Utah
2006-07, meanwhile, was a parity hodge-podge, both for teams and for players. Dirk Nowitzki won the MVP because, hey, why not? And then his Dallas team proceeded to get dismantled by the eight-seed Golden State Warriors in the first round. So that was maybe a bad choice. Meanwhile the Spurs and boring Tim Duncan coasted through the regular season (finishing 58-24, which is pretty good for coasting) only to absolutely dominate the playoffs, beating Denver 4-1, Phoenix 4-2, Utah 4-1, and sweeping LeBron's Cavaliers in the finals. Much as I hate the Spurs, Tim Duncan is, you know, really really good, and was at his best (or close) in 2006-07.
Our last two notable seasons are 1996-97 and 1997-98, responsible for two of the higher SDs in league history at .191 and .189. These were the last two seasons of the Jordan Bulls, whose dominance in the East was matched by - in the regular season anyway - the Stockton-Malone-Ostertag (joke) Jazz in the West. The NBA was kind of on cruise control in the late 90s. Parity was at an all-time low - at least since the merger - but no one seemed to mind that Utah, Miami, Chicago, Seattle, Los Angeles, and Houston were winning at or above 60 games a season while the rest of the league was mediocre or terrible. The NBA brass had to be happy, at least, because New York was at least decent, for most of the decade, meaning the huge media markets of Chicago, LA, and New York were drawing viewership, while Utah was a nice wrinkle and a good foil to the Bulls. That is, they were good enough to win a game or two, but not good enough to really challenge for the title as long as Jordan had at least one leg.
Diving into individual seasons and eras tells more about the methodology I've been using than the results. The fact is, competitiveness is subjective, and while some people will prefer parity, others prefer leagues like those of the late 90s, when parity is non-existent because a small handful of teams dominate every year. The fact is, either type of league can be successful. In Europe, the Premiership and other soccer leagues are routinely extremely top-heavy. When was the last time someone not named Chelsea, Manchester United, or Arsenal won the EPL? Answer: Blackburn Rovers in 1994-95 (during Alan Shearer's prime)*. Yeah. And yet, people keep watching even though the same three teams are at the top every year.
* And no, I won't apologize to other Americans for knowing who Alan Shearer is.
I would argue, though, that the EPL is supremely competitive for exactly that reason: there are a small set of teams that must get a result basically every match. Then there are a lot of other teams that are also well-matched, and while they're not fighting for the league title, they are trying to avoid relegation, or climb high enough to qualify for the Euro Cup, if not the European Champions League. The same is more or less true in the NBA. While, realistically, it's hard to win a seven game series against superior opposition, there's still plenty of incentive - in revenue, principally - to make the playoffs, and for better teams there's the incentive of home-court advantage that drives competition throughout the regular season.
If anything, the biggest flaw in the NBA's competitiveness in the modern era - the real cause of the larger SDs we see now - is not dilution, league size, free agency, or the salary cap. I'm sure those things contribute, but I think the biggest culprit is incentive: there's undeniably incentive for good teams to win games, but there's also incentive for bad teams to lose games. Because the NBA draft lottery is designed to give inferior teams a better chance at higher picks, tanking is all-too common, and tanking has as much effect on standard deviations of winning percentage as title chasing does. If only the NBA had a relegation system! But that's a post for another time.