Page - (000158) - in Knowledge and Networks

151 tory analysis those musicians who consistently had decreasingly betweenness centrality as of period one, and those who had consistently increasing betweenness centrality up to period eight. I included these in the Clusters 7 and 8, respectively (see Table 8.2 for the number of musicians in each cluster). Looking at Table 8.2, one can distinguish different types of trajectories and propose some tentative classifications: Cluster 1: Ivory Tower. Cluster 1 presents the second longest lifespan (6.55 peri- ods); however, it has a low presence in the core (0.7) and average betweenness is only 0.29. This suggests a group of musicians who are able to sustain themselves in the network, but have limited involvement with both the core and with other musicians. Examples of musicians in this cluster are Duke Ellington and Ella Fitzgerald. Cluster 2: Wanna-be. Musicians in Cluster 2 present the lowest betweenness aver- age (0.03), lowest lifespan (1.16), and lowest membership in the core (0.02). Unsurprisingly, it is also the largest cluster, with 3614 musicians. This is the typi- cal fate of novice musicians: After a few appearances and slammed doors, they choose to leave the industry. Cluster 3: Elite. This cluster has the longest average lifespan (6.63 periods) and the highest presence at the core (3.89 periods). It also has the second highest average betweenness centrality. I labeled the musicians “elite” because of their low num- ber (only 73 musicians), their long presence in the network, and high core pres- ence. Examples of musicians in this cluster are Dizzy Gillespie, Louis Armstrong, Miles Davis, and Stan Getz. Cluster 4: Shooting Stars. Members of this cluster have half the Elite’s average betweenness (0.52) and medium lifespan (3.88). However, they have the second highest core membership (2.26), higher than those in the Ivory Tower cluster, who presented a longer time in the network. This suggests that members of Shooting Stars, though able to remain at the core for a significant portion of their lifespan (almost 60 % of their lives), are unable to maintain their positions for as long as Elite musicians. Remarkable examples of Shooting Stars are Charlie Parker and Artie Shaw, both of whose trajectories ended prematurely. Cluster 5: Ivy League. There are only a handful of members (five) in this cluster. However, they share some interesting characteristics with other trajectory types. Like their Ivory Tower and Elite colleagues, they have a long lifespan (6.4) and a medium level of membership in the core (1.8), but the highest average between- Table 8.2 K-means cluster analysis of trajectories Cluster Key trajectory variables 1 2 3 4 5 6 Average betweenness centrality 0.29 0.03 0.98 0.52 2.80 0.13 Lifespan (periods) 6.55 1.16 6.63 3.88 6.40 3.69 Number of periods at the core 0.70 0.02 3.89 2.26 1.80 0.21 Number of individuals 180 3614 71 128 5 725 8 Trajectory Types Across Network Positions: Jazz Evolution from 1930 to 1969