Effects of League Expansion on League Strength?

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ty 4191
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Effects of League Expansion on League Strength? 

Post#1 » by ty 4191 » Sun Feb 21, 2021 2:26 pm

Hi Everyone,
I've seen this topic hit upon on various threads here; I was looking for everyone's input and expertise.

The standard deviation of winning percentage is probably the best way to measure league quality and league parity, top to bottom, over time. One way to examine this is to look at how many bad teams were in a league, over a given span of time.

Here is the modern history of NBA Expansion, current franchise name, with the number of total NBA teams in parentheses:

1961: Washington Wizards (9)
1967: Chicago Bulls (10)
1968: Houston Rockets, Seattle Supersonics (12)
1969: Milwaukee Bucks, Phoenix Suns (14)
1971: Los Angeles Clippers, Cleveland Cavaliers, Portland Trail Blazers (17)
1975: Utah Jazz (18)
1976: Denver Nuggets, Indiana Pacers, Brooklyn Nets, San Antonio Spurs (22)
1981: Dallas Mavericks (23)
1989: New Orleans Pelicans, Miami Heat (25)
1990: Minnesota Timberwolves, Orlando Magic (27)
1996: Toronto Raptors, Memphis Grizzlies (29)
2004: Charlotte Hornets (30)

Year Span, (Pre/Post Major Expansion), Spread in Winning Percentages

1960-1966:
--2 out of 9 NBA Teams (22%) below a .400 winning percentage, overall.
--0 out of 9 Teams (0%) below .300 winning percentage, overall.

1967-1973:
--4 out of 17 Teams (24%) below .400.
--3 out of 17 Teams (18%) below .300

1980-1988:
--4 out of 23 NBA Teams (17%) below .400.
--0 out of 23 NBA Teams (0%) were below .300.

1989-1998:
--10 of the 29 teams (35%) were below a .400.
--2 out of 29 teams (7%) were below .300.

2004-2021:
--3 out of 30 teams (10%) have been below a .400 winning percentage, overall.
--0 out of 30 teams (0%) were below .300.

Thoughts?

Implications??
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Re: Effects of League Expansion on League Strength? 

Post#2 » by Odinn21 » Sun Feb 21, 2021 3:03 pm

OK, I'll bite even though your previous thread is still on the front page and I know your agenda from there. It was locked before I could post my answer.

Expansions always causes distortion naturally. There's no surprises about that. If you add 2 teams to the current league, what happened in the '90s would repeat itself. If you add 2 teams in every European football league, the games would have 3-0 or worse scorelines more often because additions in real life sports are to the low end of the spectrum. Not the high end.

Here's the teams the Jordan's Bulls played against in the title years playoffs after the 1st rounds;

1990 Sixers; +4.23 SRS (6th), +5.1 NRtg (5th), +0.3 rDRtg (16th)
1990 Pistons; +5.41 SRS (4th), +6.4 NRtg (3rd), -4.6 rDRtg (2nd)
1991 Sixers; -0.39 SRS (15th), -0.2 NRtg (14th), +0.2 rDRtg (16th)
1991 Pistons; +3.08 SRS (9th), +3.5 NRtg (7th), -3.3 rDRtg (4th)
1991 Lakers; +6.73 SRS (3rd), +7.1 NRtg (3rd), -2.9 rDRtg (5th)
1992 Knicks; +3.67 SRS (7th), +4.1 NRtg (6th), -4.0 rDRtg (2nd)
1992 Cavs; +5.34 SRS (5th), +5.7 NRtg (5th), 0.0 rDRtg (11th)
1992 Blazers; +6.94 SRS (2nd), +7.3 NRtg (3rd), -4.0 rDRtg (4th)
1993 Cavs; +6.30 SRS (2nd), +6.8 NRtg (3rd), -2.0 rDRtg (6th)
1993 Knicks; +5.87 SRS (5th), +6.4 NRtg (5th), -8.3 rDRtg (1st)
1993 Suns; +6.27 SRS (3rd), +6.7 NRtg (4th), -1.3 rDRtg (9th)
1996 Knicks; +2.24 SRS (10th), +2.5 NRtg (10th), -4.1 rDRtg (4th)
1996 Magic; +5.40 SRS (5th), +6.0 NRtg (5th), -0.7 rDRtg (12th)
1996 Sonics; +7.40 SRS (2nd), +8.2 NRtg (2nd), -5.5 rDRtg (2nd)
1997 Hawks; +5.51 SRS (5th), +6.2 NRtg (4th), -4.4 rDRtg (3rd)
1997 Heat; +5.56 SRS (4th), +6.2 NRtg (5th), -6.1 rDRtg (1st)
1997 Jazz; +7.97 SRS (2nd), +9.7 NRtg (2nd), -2.7 rDRtg (9th)
1998 Hornets; +2.45 SRS (12th), +2.2 NRtg (12th), +0.3 rDRtg (15th)
1998 Pacers; +6.25 SRS (4th), +6.9 NRtg (5th), -3.4 rDRtg (5th)
1998 Jazz; +5.73 SRS (5th), +7.3 NRtg (4th), +0.4 rDRtg (17th)

Now, the impact of what you're talking about;
- The Bulls had worse 1st rounds than what should've been. But not after.
- The numbers on there can be interpreted as inflated due to expansion. But here's the kick, the rankings do not change with expansions. The playing field stayed the same for everyone involved.

Onto why you're talking about this stuff;
- Your assumption is about Michael Jordan dominating a weak league. And expansion is an issue to be addressed for the Bulls dominance. But not in the way you intended. If we look at mean and median of those ranks;
Mean SRS rank average of Bulls opponents is 5.50 over 20 playoff series.
Mean NRtg rank average of Bulls opponents is 5.35 over 20 playoff series.
Median SRS rank of Bulls opponents 5.00 over 20 playoff series.
Median NRtg rank of Bulls opponents 5.00 over 20 playoff series.
- The usual threshold for good defense is -2.0 rDRtg and for elite defense is -4.0 rDRtg. But let's kick them lower by 0.5 because expansion might have inflated those numbers too. The Bulls played against a -2.5 rDRtg or better defense 12 times. It's also 4 times against elite defenses, 2 of them being historic / atg level defenses.

So, I'd agree that expansion teams made easier for the best teams around to have great regular season records, SRS and NRtg. Their very presence also made the 1st rounds easier. But I don't see how the expansion made becoming the champion easier. The overall road might seem easier but the champions are decided after the 1st rounds (except a few outliers, such as 2014 Spurs being forced the most by the Mavs in the 1st round).
The issue with per75 numbers;
36pts on 27 fga/9 fta in 36 mins, does this mean he'd keep up the efficiency to get 48pts on 36fga/12fta in 48 mins?
The answer; NO. He's human, not a linearly working machine.
Per75 is efficiency rate, not actual production.
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Re: Effects of League Expansion on League Strength? 

Post#3 » by ty 4191 » Sun Feb 21, 2021 3:27 pm

Hi Odinn21,
Thank you for posting and for the information.

Can I inquire what the acronyms mean, and where you got the data from?

Also, how does this Bulls ran compare to, say, Lebron James' teams, in the aggregate, or Larry Bird's (pre 1988-1989 Expansion & His Injuries).

Thanks!
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Re: Effects of League Expansion on League Strength? 

Post#4 » by sansterre » Sun Feb 21, 2021 3:53 pm

ty 4191 wrote:Hi Everyone,
I've seen this topic hit upon on various threads here; I was looking for everyone's input and expertise.

The standard deviation of winning percentage is probably the best way to measure league quality and league parity, top to bottom, over time. One way to examine this is to look at how many bad teams were in a league, over a given span of time.

Here is the modern history of NBA Expansion, current franchise name, with the number of total NBA teams in parentheses:

1961: Washington Wizards (9)
1967: Chicago Bulls (10)
1968: Houston Rockets, Seattle Supersonics (12)
1969: Milwaukee Bucks, Phoenix Suns (14)
1971: Los Angeles Clippers, Cleveland Cavaliers, Portland Trail Blazers (17)
1975: Utah Jazz (18)
1976: Denver Nuggets, Indiana Pacers, Brooklyn Nets, San Antonio Spurs (22)
1981: Dallas Mavericks (23)
1989: New Orleans Pelicans, Miami Heat (25)
1990: Minnesota Timberwolves, Orlando Magic (27)
1996: Toronto Raptors, Memphis Grizzlies (29)
2004: Charlotte Hornets (30)

Year Span, (Pre/Post Major Expansion), Spread in Winning Percentages

1960-1966:
--2 out of 9 NBA Teams (22%) below a .400 winning percentage, overall.
--0 out of 9 Teams (0%) below .300 winning percentage, overall.

1967-1973:
--4 out of 17 Teams (24%) below .400.
--3 out of 17 Teams (18%) below .300

1980-1988:
--4 out of 23 NBA Teams (17%) below .400.
--0 out of 23 NBA Teams (0%) were below .300.


1989-1998:
--10 of the 29 teams (35%) were below a .400.
--2 out of 29 teams (7%) were below .300.

2004-2021:
--3 out of 30 teams (10%) have been below a .400 winning percentage, overall.
--0 out of 30 teams (0%) were below .300.

Thoughts?

Implications??

Forgive me. When you say 3 of 17 teams below .300 from '67 to '73, do you mean "when I average all the records for those seven seasons, three of the seventeen *average* below 0.300?

And from my studies, expansion doesn't lead to the kind of weakness you might guess. Actually it tends to lead to the opposite.

Expansion -> more bad teams -> good teams look better than they would otherwise be because more of their opponents are weak than would have occurred without expansion

Expansion *DOES* increase the number of wins and SRS for everybody else, making the top regular season teams appear unusually good where they might not otherwise be
Expansion *DOES NOT* decrease the number of quality teams that the top teams go up against. If anything, it increases the *appearance* of top teams by making boosting their Wins/SRS. Look at '72. The Bucks and Lakers were giants among insects that year, but expansion had gutted the bottom of the league. Those two were *definitely* the best in the league that year (and would have been with or without expansion) but they looked disproportionately good *because* of expansion.

This is a long way of saying the following:

1) Jordan's teams absolutely benefited from expansion;
2) EVERY team in the league benefited just the same;
3) The wins and SRS of Jordan's teams should be given a small grain of salt (4 new teams onto 23 is only a 17% increase, nothing close to the kind of dilution we saw in the late 60s/early 70s);
4) None of this explains why the Bulls were the *only* team to explode in the 90s - all the things that made it easier for the Bulls to look good by beating on bad teams occurred for everyone else;
5) Jordan's dominance in the playoffs had pretty much nothing to do with expansion teams, as those teams would have been the opponents irregardless, and were not weakened in any way. If anything, expansion should have made his opponents look disproportionately good.

Eras are not equal opportunity when it comes to greatness. The Celtics were pretty much a solo act (aside from '67-'69) in the late 50s and 60s. In the early 70s you had the Bucks, Lakers and Knicks, but all fell apart for different reasons and no dominant teams arose in the mid-late 70s. In the 80s the Lakers were in a cake-shaped cake conference and won it 8 of 11 years with little opposition, and in the East the Celtics were consistently strong (but were challenged early by the Sixers, late by the Pistons and generally by the Bucks). Because the Lakers happened to get the sucky conference they won a ton of Finals simply by being there more often (and by being good). In the 90s, aside from the beginning (Pistons/Lakers) and the end (Spurs) there was pretty much the Bulls and nobody else. And they won everything.

When you get a great team that *happens* to be in a league without another great team, they tend to win a ton. Look at the Celtics in the 60s. The Bulls were insanely good, but they looked better because they played in a decade with little strong opposition. And that had nothing to do with expansion. It's just how it goes sometimes. Imagine that the Kareem Bucks had existed in the mid-late 70s? They'd have won 3 or 4. And they'd be considered a dynasty. They just happened to get plopped in an era with other great teams.

Jordan played in an era weirdly low on strong challengers. It had nothing to do with expansion.
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Re: Effects of League Expansion on League Strength? 

Post#5 » by Odinn21 » Sun Feb 21, 2021 4:11 pm

ty 4191 wrote:Hi Odinn21,
Thank you for posting and for the information.

Can I inquire what the acronyms mean, and where you got the data from?

Also, how does this Bulls ran compare to, say, Lebron James' teams, in the aggregate, or Larry Bird's (pre 1988-1989 Expansion & His Injuries).

Thanks!

SRS (Simple Rating System) is a method to determine a teams strength in numbers from MoV (Margin of Victory). The formula;
SRS = MoV + SoS (Strength of Schedule)
SoS accounts for the results available at that moment. Here's how the idea of SoS and SRS work;
Imagine a team that started the season with 2-12 record and -8.2 MoV per game. Defeating that team is not a big challenge at that point. But they get their sh.t together, go on a run and by the mid season, they stand at 23-28 record with -3.5 MoV per game. At that point, they are a bigger challenge.
SoS basically accounts for that. Evaluation of a team's opponents based on the results at times games were played.

NRtg is a calculation for changes in pace.
Assume a team has +3.5 MoV in a season and they played their games on a 92.2 pace (meaning they averaged 92.2 possessions for 48 minutes).
And imagine another team with +3.5 MoV but on a pace of 103.0.
They are not the same, are they?
NRtg simply calculates for 100 possessions in 48 minutes. The former example has a NRtg of +3.8 and the latter example has a NRtg of +3.4.
NRtg = ORtg - DRtg (ORtg is derived from points scored and DRtg is derived from points allowed.)

rDRtg means relative DRtg which is used for changing efficiency numbers from season to season.
DRtg average in 1992-93 regular season was 108.0.
DRtg average in 1997-98 regular season was 105.0.
DRtg average in 2019-20 regular season was 110.6.

A DRtg of 107.5 would be slightly an above average defense in 1992-93 season, would be a bad defense in 1997-98 and would be a good defense in 2019-20 regular season.

rDRtg is just simply team's DRtg - season average to see how a team differentiated itself from the average to see how good their defense was in reality.

https://www.basketball-reference.com/
This is the website. It has many stuff to discover for you. I'd suggest you to start with glossary to get familiar with the acronyms.

I actually prefer team stats on NBA.com over BBRef but NBA.com stats go as far as 1996-97 because that's the season full logs are available with on/off court records. BBRef however goes back as far as 1983-84 season with full logs minus on/off court records. They also basically have all the team logs with pts/reb/ast numbers and field goal attempts.

I don't want to go over James' and Bird's track record in the playoffs. But the gist is, James' teams faced a weak competition in the EC from 2014 to 2018. Though considering how his teams got gradually worse over time after the initial conception, it shouldn't be right to blame it on James. Bird's teams faced one of the best competition there was. The '80s East was loaded. From 1984 to 1988, the Celtics faced a top 5 SRS team 8 times out of 10 series past 1st round in the conference. But then again, with such competition, Bird's teams didn't get to accomplish as much as Jordan's teams or James' teams.
The issue with per75 numbers;
36pts on 27 fga/9 fta in 36 mins, does this mean he'd keep up the efficiency to get 48pts on 36fga/12fta in 48 mins?
The answer; NO. He's human, not a linearly working machine.
Per75 is efficiency rate, not actual production.
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Re: Effects of League Expansion on League Strength? 

Post#6 » by penbeast0 » Sun Feb 21, 2021 4:57 pm

Thank you for post this ty . . . I hope Odinn hasn't turned this back into a Jordan thread because it's an interesting question and one we have a number of opinions on.

The most common method here is comparing the number of teams to the number of adult males that those teams commonly draw from thus taking into account not only expansion, but the baby boom, and the influx of world talent. Using this method, your numbers would probably overestimate most 20th century teams as world talent was rarer, particularly shorter players (it was easier to scout and teach 7 footers as they stand out in any crowd so the league brought in world talent at the center spot much earlier). It would also slightly overestimate the early 60s when top end black talent was coming into the league but end of benches were kept white deliberately and more significantly overestimate 72-76 when the ABA was drawing off significant levels of talent (before that the ABA stars either weren't really top quality NBA stars except for Rick Barry and probably Mel Daniels or were players banned from the NBA like Roger Brown and Doug Moe -- they made an exception to let Connie Hawkins jump leagues after 69).
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Re: Effects of League Expansion on League Strength? 

Post#7 » by Odinn21 » Sun Feb 21, 2021 5:02 pm

penbeast0 wrote:Thank you for post this ty . . . I hope Odinn hasn't turned this back into a Jordan thread because it's an interesting question and one we have a number of opinions on.

Ah, I guess you're right to put it that way. Like I said, I was typing a similar response for the previous thread but you locked that one before I got to submit my post. So I carried the impression I got on there. I don't know if it's an inconvenience, but if it is, my apologies.
The issue with per75 numbers;
36pts on 27 fga/9 fta in 36 mins, does this mean he'd keep up the efficiency to get 48pts on 36fga/12fta in 48 mins?
The answer; NO. He's human, not a linearly working machine.
Per75 is efficiency rate, not actual production.
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Re: Effects of League Expansion on League Strength? 

Post#8 » by penbeast0 » Sun Feb 21, 2021 5:08 pm

Not an inconvenience, I just genuinely wanted/want to hear about how we evaluate league strength and if we turn this into just another "MJ is GOAT" thread then I don't think we will ever get that discussion.
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Re: Effects of League Expansion on League Strength? 

Post#9 » by Odinn21 » Sun Feb 21, 2021 5:35 pm

penbeast0 wrote:Not an inconvenience, I just genuinely wanted/want to hear about how we evaluate league strength and if we turn this into just another "MJ is GOAT" thread then I don't think we will ever get that discussion.

In terms of spikes, expansion caused big spikes in SRS values even with the lack of utilization of threes (or even existence of threes).

Here's some more numbers;
1965-66 reg. season SRS leader - the Celtics with +4.34
* Chicago Bulls added to the league.
1966-67 reg. season SRS leader - the Sixers with +8.50 [Chi -3.37 SRS]
* San Diego Rockets and Seattle SuperSonics added to the league.
1967-68 reg. season SRS leader - the Sixers with +7.96 [SD -7.94 & Sea -6.00 SRS]
* Phoenix Suns and Milwaukee Bucks added to the league.
1968-69 reg. season SRS leader - the Knicks with +5.48 [Pho -8.26 & Mil -5.07 SRS]
1969-70 reg. season SRS leader - the Knicks with +8.42
* Buffalo Braves, Cleveland Cavaliers and Portland Trail Blazers added to the league.
1970-71 reg. season SRS leader - the Bucks with +11.92 [Buf -8.02, Cle -12.04 & Por -6.20 SRS]
1971-72 reg. season SRS leader - the Lakers with +11.65

This was the first big expansion era the NBA experienced. It was a unique time already with existence of the ABA, I wouldn't assume the merger as an expansion because the teams joined the NBA already had organizations up and running.

The second big expansion era was from 1988 to 1995.
1987-88 reg. season SRS leader - the Celtics with +6.15
* Miami Heat and Charlotte Hornets added to the league.
1988-89 reg. season SRS leader - the Cavs with +7.95 [Mia -11.13 & Cha -7.74 SRS]
* Minnesota Timberwolves and Orlando Magic added to the league.
1989-90 reg. season SRS leader - the Suns with +7.09 [Min -3.60 & Orl -8.73 SRS]
1990-91 reg. season SRS leader - the Bulls with +8.57
1991-92 reg. season SRS leader - the Bulls with +10.07
1992-93 reg. season SRS leader - the Sonics with +6.66
1993-94 reg. season SRS leader - the Sonics with +8.68
1994-95 reg. season SRS leader - the Sonics with +7.91
* Vancouver Grizzlies and Toronto Raptors added to the league.
1995-96 reg. season SRS leader - the Bulls with +11.80 [Van -9.55 & Tor -7.20 SRS]
1996-97 reg. season SRS leader - the Bulls with +10.70

Other than Chicago Bulls, in every single one of the expansion teams was the worst team in the league. Heck, that 3 teams of '70 expansion, they were the bottom 3 in their first season in the league.

The only thing other than the expansions caused such spikes is utilization of three pointers as the margins started to get differentiate on a bigger scale.
The issue with per75 numbers;
36pts on 27 fga/9 fta in 36 mins, does this mean he'd keep up the efficiency to get 48pts on 36fga/12fta in 48 mins?
The answer; NO. He's human, not a linearly working machine.
Per75 is efficiency rate, not actual production.
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Re: Effects of League Expansion on League Strength? 

Post#10 » by ty 4191 » Sun Feb 21, 2021 5:59 pm

sansterre wrote:Forgive me. When you say 3 of 17 teams below .300 from '67 to '73, do you mean "when I average all the records for those seven seasons, three of the seventeen *average* below 0.300?

Jordan played in an era weirdly low on strong challengers. It had nothing to do with expansion.


Yes, that's what I meant. I mean, aggregate winning percentages for each franchise. There were FAR more "long term very weak teams" from 1989-1998 than there were 1978-1988.

Also, I'm failing to see how this is NOT largely attributable to adding 6 new (perpetually lousy) teams into a 23 team league between 1989 and 1996.

How does one determine league strength- statistically- between eras, other than running the standard deviation of winning percentage in each league to determine top to bottom parity?
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Re: Effects of League Expansion on League Strength? 

Post#11 » by sansterre » Sun Feb 21, 2021 6:15 pm

ty 4191 wrote:
sansterre wrote:Forgive me. When you say 3 of 17 teams below .300 from '67 to '73, do you mean "when I average all the records for those seven seasons, three of the seventeen *average* below 0.300?

Jordan played in an era weirdly low on strong challengers. It had nothing to do with expansion.


Yes, that's what I meant. I mean, aggregate winning percentages for each franchise. There were FAR more "long term very weak teams" from 1989-1998 than there were 1978-1988.

Also, I'm failing to see how this is NOT largely attributable to adding 6 new (perpetually lousy) teams into a 23 team league between 1989 and 1996.

How does one determine league strength- statistically- between eras, other than running the standard deviation of winning percentage in each league to determine top to bottom parity?

There are two different arguments that you could be making. Would you help me understand which it is?

Argument #1: "Expansion reduced the average level of quality per team in the league, making it easier to win lots of games and dominate the regular season."

Argument #2: "Expansion reduced the average level of quality per team in the league, reducing the number of strong teams that could contend for the championship and so making it easier to win the championship for the best teams."

The data absolutely supports #1.

I don't think the data supports #2. Adding lots of bad teams to the league makes the regular season easier to dominate, but by the playoffs those teams are pretty much out of it.

So I agree with you that expansion was, largely, the driving force of those aberrantly bad team records.
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Re: Effects of League Expansion on League Strength? 

Post#12 » by ty 4191 » Sun Feb 21, 2021 6:23 pm

sansterre wrote:There are two different arguments that you could be making. Would you help me understand which it is?

Argument #1: "Expansion reduced the average level of quality per team in the league, making it easier to win lots of games and dominate the regular season."

Argument #2: "Expansion reduced the average level of quality per team in the league, reducing the number of strong teams that could contend for the championship and so making it easier to win the championship for the best teams."

The data absolutely supports #1.

I don't think the data supports #2. Adding lots of bad teams to the league makes the regular season easier to dominate, but by the playoffs those teams are pretty much out of it.

So I agree with you that expansion was, largely, the driving force of those aberrantly bad team records.


Mainly, Argument #1.

Also, re: Argument #2, that superstars of ANY era, where 30%+ of the teams are under .400, overall, and some are even under .300, for many years...are ALL tremendously overrated as players.
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Re: Effects of League Expansion on League Strength? 

Post#13 » by ty 4191 » Sun Feb 21, 2021 6:26 pm

Which leagues in NBA history were the strongest (and/or) most balanced, and which were the weakest (and/or) least balanced, overall?

And, how do we determine this, statistically?
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Re: Effects of League Expansion on League Strength? 

Post#14 » by sansterre » Sun Feb 21, 2021 6:26 pm

ty 4191 wrote:
sansterre wrote:Mainly, Argument #1.

Also, re: Argument #2, that superstars of ANY era, where 30%+ of the teams are under .400, overall, and some are even under .300, for many years...are ALL tremendously overrated as players.

I think that 'tremendously' is a clear exaggeration. But I think it's a fair point that we should take regular season numbers of players with a little caution. But playoff numbers should be taken pretty seriously, as the quality by that point should be reasonably comparable to other eras.
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Re: Effects of League Expansion on League Strength? 

Post#15 » by sansterre » Sun Feb 21, 2021 6:27 pm

ty 4191 wrote:Which leagues in NBA history were the strongest (and/or) most balanced, and which were the weakest (and/or) least balanced, overall?

And, how do we determine this, statistically?

I favor using the standard deviation of the SRSs of the year. 1972 comes out far and away the least competitive year by this standard, while years in the mid-late 70s come out extremely competitive.
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Re: Effects of League Expansion on League Strength? 

Post#16 » by ty 4191 » Sun Feb 21, 2021 6:49 pm

sansterre wrote:I favor using the standard deviation of the SRSs of the year. 1972 comes out far and away the least competitive year by this standard, while years in the mid-late 70s come out extremely competitive.


Sansterre,
Thank you for your input.

Re: Mid/Late 70's....is this because the ABA/NBA Merger created the strongest/deepest league, to date (at that time) and perhaps, in NBA History?

How do the decades rank in standard deviation of SRS?
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Re: Effects of League Expansion on League Strength? 

Post#17 » by penbeast0 » Sun Feb 21, 2021 6:58 pm

In terms of playoffs, you would have to look at the % of teams in the league that made the playoffs as well as the above numbers. It should eliminate the expansion teams, yes, a year where 1/2 the teams made the playoffs (just like the year before) but where the number of teams had expanded by 4 would probably have significantly weaker teams in the playoffs. You basically added 2 of the teams that would have missed the playoffs the year before even though neither of them will be expansion teams. They will look stronger because they beat up on the expansion teams but if anything they will probably be a bit weaker because the expansion teams pulled some of the bench talent off everywhere.
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Re: Effects of League Expansion on League Strength? 

Post#18 » by sansterre » Sun Feb 21, 2021 8:55 pm

ty 4191 wrote:
sansterre wrote:I favor using the standard deviation of the SRSs of the year. 1972 comes out far and away the least competitive year by this standard, while years in the mid-late 70s come out extremely competitive.


Sansterre,
Thank you for your input.

Re: Mid/Late 70's....is this because the ABA/NBA Merger created the strongest/deepest league, to date (at that time) and perhaps, in NBA History?

How do the decades rank in standard deviation of SRS?


You'd think the merger drove it, but the STDEV plummeted in ''75 and '76 and stayed low until '80. So I'd read it less as "the merger drove it" and more as "Kareem went to a bad team, West and Wilt were gone, the Knicks had aged out and the league didn't inherit any more transcendent talent until Bird and Magic came along."

Here are the standard deviations for each year, but this is my OSRS (v1) not regular season SRS, so take it with a grain of salt (sorry, pasted from excel):

1955 2.4
1956 3.26
1957 3.08
1958 4.2
1959 4.97
1960 4.91
1961 4.38
1962 4.85
1963 4.25
1964 5.09
1965 3.93
1966 3.77
1967 5.47
1968 4.45
1969 4.86
1970 3.85
1971 5.82
1972 6.74
1973 5.96
1974 4.02
1975 3.69
1976 2.46
1977 3.22
1978 3.04
1979 3.35
1980 4.29
1981 4.4
1982 4.35
1983 4.93
1984 3.47
1985 4.5
1986 4.96
1987 5.03
1988 4.81
1989 5.69
1990 5.07
1991 5.22
1992 5.16
1993 4.87
1994 5.23
1995 4.99
1996 5.6
1997 5.56
1998 5.53
1999 4.79
2000 4.7
2001 4.93
2002 4.3
2003 4.43
2004 4.57
2005 4.44
2006 4.11
2007 3.97
2008 5.38
2009 5.35
2010 5
2011 4.68
2012 5.29
2013 4.91
2014 4.99
2015 5.15
2016 5.76
2017 4.92
2018 4.52
2019 5.44
2020 5.38

Here are the graphs for those numbers, and then one smoothed by 3yr clumps:

https://imgur.com/ZrS5Hsv (1yr)

https://imgur.com/uWSypDG (3yr)

Here are the three-year averages from after each expansion:

1961: 4.49
1967: 4.93
1968: 4.39
1969: 4.84
1971: 6.17
1975: 3.12
1976: 2.91
1981: 4.56
1989: 5.33
1990: 5.15
1996: 5.56
2004: 4.37

3yr Trailing Average Expansion Years: 4.65
3yr Trailing Non-Expansion Years: 4.67
3yr Trailing Non-Expansion pre-2004: 4.48

This is a really, really long way of saying: "Yes, it has effects . . . but they're not as big as you might guess."
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Re: Effects of League Expansion on League Strength? 

Post#19 » by Odinn21 » Sun Feb 21, 2021 9:35 pm

Odinn21 wrote:1969-70 reg. season SRS leader - the Knicks with +8.42
* Buffalo Braves, Cleveland Cavaliers and Portland Trail Blazers added to the league.
1970-71 reg. season SRS leader - the Bucks with +11.92 [Buf -8.02, Cle -12.04 & Por -6.20 SRS]

Wanted to expand on this particular example.

First, I should start with clearing that 1971 Bucks is a goat level team. There's no doubt about it.
However, 1970 Knicks were also an insanely strong team in the previous season and they were almost at 8 SRS mark. And more importantly, that 40+% jump just would not happen out of the blue in under normal circumstances.

Here's further numbers;
In 1970-71 reg. season, the Bucks played
4 games against the Braves and won all of them by +18.5 MoV
4 games against the Cavs and won all of them by +27.8 MoV
4 games against the Blazers and won 3 of them by +12.0 MoV

In the 12 games the Bucks played against expansion teams; 11-1 record & +19.42 MoV
In the 70 games the Bucks played against existing teams; 55-15 record & +11.03 MoV

Now, there's also another thing to consider; addition of the new teams changed the distribution of the schedule.
SRS considers SoS but not enough to correct such an extent. The Bucks had 23.2% of their MoV in 14.6% of their game.

For the '96 Bulls, it was different than this because there was more teams around meaning that distribution of the schedule did not get changed that heavily.
The issue with per75 numbers;
36pts on 27 fga/9 fta in 36 mins, does this mean he'd keep up the efficiency to get 48pts on 36fga/12fta in 48 mins?
The answer; NO. He's human, not a linearly working machine.
Per75 is efficiency rate, not actual production.
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Re: Effects of League Expansion on League Strength? 

Post#20 » by DQuinn1575 » Mon Feb 22, 2021 4:47 am

sansterre wrote:
ty 4191 wrote:
sansterre wrote:I favor using the standard deviation of the SRSs of the year. 1972 comes out far and away the least competitive year by this standard, while years in the mid-late 70s come out extremely competitive.


Sansterre,
Thank you for your input.

Re: Mid/Late 70's....is this because the ABA/NBA Merger created the strongest/deepest league, to date (at that time) and perhaps, in NBA History?

How do the decades rank in standard deviation of SRS?


You'd think the merger drove it, but the STDEV plummeted in ''75 and '76 and stayed low until '80. So I'd read it less as "the merger drove it" and more as "Kareem went to a bad team, West and Wilt were gone, the Knicks had aged out and the league didn't inherit any more transcendent talent until Bird and Magic came along."

Here are the standard deviations for each year, but this is my OSRS (v1) not regular season SRS, so take it with a grain of salt (sorry, pasted from excel):

1955 2.4
1956 3.26
1957 3.08
1958 4.2
1959 4.97
1960 4.91
1961 4.38
1962 4.85
1963 4.25
1964 5.09
1965 3.93
1966 3.77
1967 5.47
1968 4.45
1969 4.86
1970 3.85
1971 5.82
1972 6.74
1973 5.96
1974 4.02
1975 3.69
1976 2.46
1977 3.22
1978 3.04
1979 3.35
1980 4.29
1981 4.4
1982 4.35
1983 4.93
1984 3.47
1985 4.5
1986 4.96
1987 5.03
1988 4.81
1989 5.69
1990 5.07
1991 5.22
1992 5.16
1993 4.87
1994 5.23
1995 4.99
1996 5.6
1997 5.56
1998 5.53
1999 4.79
2000 4.7
2001 4.93
2002 4.3
2003 4.43
2004 4.57
2005 4.44
2006 4.11
2007 3.97
2008 5.38
2009 5.35
2010 5
2011 4.68
2012 5.29
2013 4.91
2014 4.99
2015 5.15
2016 5.76
2017 4.92
2018 4.52
2019 5.44
2020 5.38

but they're not as big as you might guess."


Average of years above with Expansion (per original poster, not counting ABA year) = 4.90
Average of all years in 21st century, except for 1 expansion year =4.88

You also see a year like 2007-2008 where the StDev above goes from 3.97 to 5.38 - one of the biggest jumps.

Standard Deviation of SRS is not a measure of league strength.

It's demographics of population - size of pool in playing age, international play, quotas in early years, playing coming into the league earlier, and impact of other leagues - not only ABA, but in early days AAU ball.

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