Relative Citation Ratio (RCR): A New Metric That Uses Citation Rates to Measure Influence at the Article Level
(A) Schematic of a co-citation network. The reference article (RA) (red, middle row) cites previous papers from the literature (orange, bottom row); subsequent papers cite the RA (blue, top row). The co-citation network is the set of papers that appear alongside the article in the subsequent citing papers (green, middle row). The field citation rate is calculated as the mean of the latter articles’ journal citation rates. (B) Growth of co-citation networks over time. Three RAs published in 2006 (red dots) were cited 5 (top row), 9 (middle row), or 31 times (bottom row) by 2011. Three intervals were chosen to illustrate the growth of the corresponding co-citation networks: 2006–2007, 2006–2009, and 2006–2011 (the first, second, and third columns, respectively). Each article in one of the three co-citation networks is shown as a separate green dot; the edges (connections between dots) indicates their presence together in the same reference list. (C) Cluster algorithm-based content analysis of the 215 papers in the co-citation network of a sample RA (panel B, bottom network series) identified a changing pattern of relevance to different subdisciplines over time. This RA described the identification of new peptides of possible clinical utility due to their similarity to known conotoxins. Papers in the co-citation network of this RA focused on (1) α-conotoxin mechanisms of action, (2) structure and evolution of conotoxins, (3) cyclotide biochemistry, (4) conotoxin phylogenetics, and (5) identification and synthesis of lantibiotics. (D) Growth of an article’s co-citation network is proportional to the number of times it has been cited. Each point is the average network size of 1,000 randomly chosen papers with between 1 and 100 citations (error bars represent the standard error of the mean). Each paper is only counted once, even if it is co-cited with the article of interest multiple times. An average of 17.8 new papers is added to the co-citation network for each additional citation. This suggests substantial duplication of articles within a co-citation network, since on average 32.4 papers (median of 30) are referenced in each citing article.