title: Estimates of the continuously publishing core in the scientific workforce.
abstract: BACKGROUND
  The ability of a scientist to maintain a continuous stream of publication may be important, because research requires continuity of effort. However, there is no data on what proportion of scientists manages to publish each and every year over long periods of time.
  
  
  RESULTS
  Using the entire Scopus database, we estimated that there are 15,153,100 publishing scientists (distinct author identifiers) in the period 1996-2011. However, only 150,608 (<1%) of them have published something in each and every year in this 16-year period (uninterrupted, continuous presence [UCP] in the literature). This small core of scientists with UCP are far more cited than others, and they account for 41.7% of all papers in the same period and 87.1% of all papers with >1000 citations in the same period. Skipping even a single year substantially affected the average citation impact. We also studied the birth and death dynamics of membership in this influential UCP core, by imputing and estimating UCP-births and UCP-deaths. We estimated that 16,877 scientists would qualify for UCP-birth in 1997 (no publication in 1996, UCP in 1997-2012) and 9,673 scientists had their UCP-death in 2010. The relative representation of authors with UCP was enriched in Medical Research, in the academic sector and in Europe/North America, while the relative representation of authors without UCP was enriched in the Social Sciences and Humanities, in industry, and in other continents.
  
  
  CONCLUSIONS
  The proportion of the scientific workforce that maintains a continuous uninterrupted stream of publications each and every year over many years is very limited, but it accounts for the lion's share of researchers with high citation impact. This finding may have implications for the structure, stability and vulnerability of the scientific workforce.
authors.affiliation: Departments of Medicine, Health Research and Policy, and Statistics, Stanford University, Stanford, California, United States of America.
authors.forename: John P A
authors.initials: JP
authors.lastname: Ioannidis
authors.affiliation: SciTech Strategies, Inc., Albuquerque, New Mexico, United States of America.
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Boyack
authors.affiliation: SciTech Strategies, Inc., Berwyn, Pennsylvania, United States of America.
authors.forename: Richard
authors.initials: R
authors.lastname: Klavans
mesh_terms: D015706:Bibliometrics; D035843:Biomedical Research / Q000706:statistics & numerical data; D005060:Europe; D006801:Humans; D009656:North America; D017712:Peer Review, Research; D010506:Periodicals as Topic / Q000706:statistics & numerical data; D012108:Research Personnel / Q000706:statistics & numerical data*; D012942:Social Sciences / Q000706:statistics & numerical data; D000078329:Workforce