In response to the questions and comments on my previous post on ages and success in the NBA, I did a little additional work. I could not do everything that people asked about, but I tried to improve the previous analysis in four ways:
1. More Data!
It is relatively easy to download the entire statistical history of the NBA at databaseBasketball.com. Minutes played data "only " go back to the 1950-51, so that is the earliest season included below. It also does not include the current season, but I manually added the 2008-2009 Blazers. The coolest thing about having older data is that it gives us a target for a (somewhat goofy) record: the best record for a team whose average age is under 25 in the (modern) history of the NBA.
2. Better Measurement of Age
The databaseBasketball.com data has players' date of birth, which makes it easy to get calculate their age to the day (ie. 24.53 years rather than 24). Each player's age for each season is determined by their age on December 31st of the given season. This may not seem like a big deal, but it actually made this year's Blazers about half a year older.
3. Years of Experience
Several people were interested in seeing the results if the measurement of maturity was years of experience, rather than age. I measured experience in two ways. The first, which I refer to as "Years of Experience" is just the number of seasons since their first seasons in the league, counting their rookie season as their first season. So, if a player's first season in the league was 1990, they would have one year of experience in the 1990 seasons and six years of experience in the 1995 season. The weakness of this measure is that it counts a year of experience whether or not a player played any games. So, I created a second measure, referred to as "Years of Game Experience" that counts a season of experience as playing 77 games. Why 77 and not 82? It's actually fairly rare for anyone to play all 82 games of a season. Why 77 rather than 72? In short, I just picked a number, but since everyone's years are scaled in the same way it does not matter too much. In addition, the two measures ("years of experience" and "years of game experience") tracked fairly closely for star players like Kareem or Bird when I used 77 games.
4. Tracking Team Trajectories
A lot of people were interested in seeing the trajectories of particular teams over time. As you will see, I tracked a few team trajectories in only the most simplistic way: a did three seperate graphs that highlighted the team-age relationships for three franchises: the Blazers, Lakers, and Clippers. For those that really want to try to make projections about the future, this is probably not enough. It is, however, fun to see. Moreover, I did not see an obvious way to use the data to make projections that would be any more definitive than what we would all do in our heads.
Win % by Average Age, 1951 to 2009
So, what are the results? First, I plotted win percentage by the average age of the team on the floor. I also drew a line for the average win% pct given average age, just for reference. For an explanation of how I calculated average age and drew the line, go here... The two best under 25 teams are in red. This first graph is almost too awesome to believe. Keep in mind that this is after the Blazers lost two games in a row... and comes with the Blazers having played a brutal schedule so far (the graph looked even crazier before last night's game):
Yes, this year's Blazers top competition for best record by a team whose average age was under 25 years is the 1976-1977 Portland Trailblazers. Here is a link to see the ages and minutes played for that legendary Portland team. 1977 was the year I was born, so I did not know that that team had a relatively pedestrian regular season record. Obviously, that is also the youngest team to ever win an NBA championship. That's one achievement that I do not think this year's team can match.
Win % by Years in the League, 1951 to 2009
How do the 2008-2009 Blazers compare when maturity is measured by years experience in the NBA? In some way this helps this year's team because of one of it's rookies, Rudy Fernandez, is an older rookie. On the other hand, Travis Outlaw and Aldridge have a lot of NBA experience for their age. As in the previous graph, in the graph below, I plotted win% by the average years of experience for the team. I highlighted in purple the teams with the best record and an average of less than 4 years of experience:
First, note that when maturity is measured by years of experience rather than age, there is still a fairly strong maturity-success relationship. Second, there are actually a few teams more exceptional than the Blazers, including the 1991-1992 Golden State Warriors with Mullin, Hardaway, and Marciulionis and the 1970-1971 Milwaukie Bucks with Oscar Robertson and Kareem in his second season. That being said, the 2008-2009 Blazers are doing remarkably well by this measure.
Win % by Years of NBA Game Experience, 1951 to 2009
As I said above, I thought that these results might be misleading if a player hardly played his first few seasons or missed a season or two with an injury. While some experience can be gained from just being around the team and practicing, most people think game experience is what players need and what this year's team needs. In addition, this year's Blazers are doing well early in the season even with three rookies seeing significant minutes. The graph below follows the same format as the previous two, but with the best teams with less than an average of 3 years game experience in green:
My guess is that this measurement of experience probably exaggerates the Blazer youth to some extent, but still reinforces that the success of the team is pretty extraordinary.
Team Trajectories: Blazers, LA-Lakers, and LA-Clippers
Lastly, I thought it would be fun to look at a few franchises in isolation/comparison. Tominhawaii joked that I should color code the teams and use their logos, which gave me an idea for how to display team trajectories and patterns. Since the graphs can can cluttered really quickly, I just did three seperate graphs for three fairly familiar franchises: the Blazers, LA Lakers, and LA Clippers (the Minneopolis Lakers and San Diego Clippers are considered separate teams in the databaseBasketball.com data and I did not see any reason to change things). Obviously, I could have done more teams or restricted any team to a particular era, but looking at just these three teams says enough. In all three graphs, I plotted the average age against win%, as in the first graph in this post. It's best to look at the three graphs together.
To lift your spirits, I put the Clippers after the Blazers:
I found myself tracing the history of the Blazers from year to year by connecting the dots in my head. Try it, I think you'll find it enjoyable.
Analytically, these three graphs strongly suggest that if one were to account for "franchise effects" or "GM effects" the age-success relationship would be even stronger. I'll leave the rest of the commentary to you.