For a while now I’ve wanted to start mucking with the free open source software (FOSS) stats and graphing program R. I needed a dataset to mess around, so I scraped the season box scores for every NBA regular season from 1950 to 2010 from basketball-reference.com.

I used Python to calculate an average age for each team by weighting each player’s age by the proportion of minutes played compared to the team’s total minutes for the regular season. For calculation purposes I use the player’s integer age on February 1st of the season.

The interesting thing about this data is to isolate the championship teams and see the age trends for the different dynasties. From the 1950s to the 1990s, each team gets older as it continues to win championships. This is not surprising, as each dynasty has a core of star players who get a year older each season. These core players play the majority of minutes, and heavily weight the average age. Both role players and bench players are usually recycled, with older ones being replaced by younger ones. This is why we can see that the average age goes up by less than a year for each consecutive season.

The Celtics Dynasty of the 1950s and 1960s starts in 1957 and goes to 1969, a stretch of 13 seasons where they won 11 championships, beating the Lakers in the Finals seven times. The Celtics were 27.0 in 1957, and 30.4 in 1969. Their 1969 team was the oldest ever to win a championship until the last two Michael Jordan Bulls’ teams of 1997 and 1998 who were the oldest ever.

The Larry Bird Celtics won the championship three times between 1981 and 1986, a period where they aged from 27.0 to 29.3. The Showtime Lakers won 5 times between 1980 and 1988, where they aged from 26.2 to 28.9. The Lakers’ increase wasn’t consistent, most likely due to the decreasing minutes of Kareem Abdul Jabbar who was 40 in 1988, and one of the oldest players ever to provide a meaningful contribution to his team (18.2 ppg, 10.9 rebs in 1988) at that age.

The Bulls teams of the 1990s won three-peats between 1991-1993, and again in 1996-1998 after Jordan’s first retirement and comeback. The first Bulls championship team of 1991 was young, just 26.9. In 1992 and 1993, they were 27.6 and 28.0 respectively. Starting with their second three-peat in 1996, they were already one of the oldest championship teams ever. I don’t think the Bulls could have won that second three-peat if not for the year and a half Jordan took off from basketball and ‘rested’ his legs playing baseball. It is inconceivable that Jordan could have played a near decade of 100 plus games and still manage to win six championships. In retrospect, when examining his age and Bulls’ age during that second three-peat, his first retirement was an ingenious move. The only other player on all six championship teams was Scottie Pippen, who didn’t take any time off in the 1990s, and who nearly carried the Bulls sans Jordan to the Eastern Conference Finals in 1994. During the championship run of the 1990s, Pippen managed to average 79 games started a season until the 1998 championship season, where age and fatigue finally caught up with him and he only started 44 games.

The Bulls broke up after the 1998 season, and the entire city of Chicago vilified general manager Jerry Krause for not bringing back the team nucleus of Coach Phil Jackson, Michael Jordan and Scottie Pippen. The Bulls were probably too old and tired to win again in 1999, but no one knew that 1999 would be a lockout-shortened 50 game season. The shortened season and the extra three months of rest would have been exactly what the very old, hypothetical 1999 Bulls needed for a chance for the first 4-peat since the 1960s Celtics.

The San Antonio Spurs won four times between 1999 and 2007, and if we exclude the anomalous 1999 lockout season, they show the same pattern of getting older.

The only exception so far is the three-peat Shaq and Kobe Lakers of the early 2000s, who actually got younger. The two-time defending championship Lakers of 2009-2010 have aged from 27.4 to 28.4, and are 30.3, more than a year older from 2010 through 57 games of the 2011 season. Out of the top eight Lakers players as measured by minutes played, 7 of them are 30 or over. This year looks like the last gasp of the current Lakers team and Kobe Bryant, with Phil Jackson set to retire and the nucleus (Bryant, Gasol, Odom, Fisher, and Artest) all 30 or over.

For the R code used for this graph and the full final season box scores for all teams, click here.