Figure 3

Illustration of the relationship between excess reciprocity and long-term career impact. (a) Centroids of the clusters identified by k-means based on the cumulative number of citations received by authors who started their career between 1970 and 1990. The sample contains 5070 authors, and the fraction of authors falling within each cluster are as follows: 1.2% in group 1, 6.9% in group 2, 24.5% in group 3, 67.4% in group 4. (b) Excess reciprocity, defined as per Eq. (1), within each cluster. Thick solid lines denote the average within the cluster, while ribbon bands denote 95% confidence level intervals