title: Concentration of the most-cited papers in the scientific literature: analysis of journal ecosystems.
abstract: BACKGROUND
  A minority of scientific journals publishes the majority of scientific papers and receives the majority of citations. The extent of concentration of the most influential articles is less well known.
  
  
  RESULTS
  The 100 most-cited papers in the last decade in each of 21 scientific fields were analyzed; fields were considered as ecosystems and their "species" (journal) diversity was evaluated. Only 9% of journals in Journal Citation Reports had published at least one such paper. Among this 9%, half of them had published only one such paper. The number of journals that had published a larger number of most-cited papers decreased exponentially according to a Lotka law. Except for three scientific fields, six journals accounted for 53 to 94 of the 100 most-cited papers in their field. With increasing average number of citations per paper (citation density) in a scientific field, concentration of the most-cited papers in a few journals became even more prominent (p<0.001). Concentration was unrelated to the number of papers published or number of journals available in a scientific field. Multidisciplinary journals accounted for 24% of all most-cited papers, with large variability across fields. The concentration of most-cited papers in multidisciplinary journals was most prominent in fields with high citation density (correlation coefficient 0.70, p<0.001). Multidisciplinary journals had published fewer than eight of the 100 most-cited papers in eight scientific fields (none in two fields). Journals concentrating most-cited original articles often differed from those concentrating most-cited reviews. The concentration of the most-influential papers was stronger than the already prominent concentration of papers published and citations received.
  
  
  CONCLUSIONS
  Despite a plethora of available journals, the most influential papers are extremely concentrated in few journals, especially in fields with high citation density. Existing multidisciplinary journals publish selectively most-cited papers from fields with high citation density.
authors.affiliation: Clinical and Molecular Epidemiology Unit, Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, Ioannina, Greece. jioannid@cc.uoi.gr
authors.forename: John P A
authors.initials: JP
authors.lastname: Ioannidis
mesh_terms: D055811:Journal Impact Factor; D010506:Periodicals as Topic / Q000706:statistics & numerical data; D012586:Science