title: Survey of the h index for all of academic neurosurgery: another power-law phenomenon?
abstract: OBJECTIVE
  The h index is a recently developed bibliometric that assesses an investigator's scientific impact with a single number. It has rapidly gained popularity in the physical and, more recently, medical sciences.
  
  
  METHODS
  The h index for all 1120 academic neurosurgeons working at all Electronic Residency Application Service-listed training programs was determined by reference to Google Scholar. A random subset of 100 individuals was investigated in PubMed to determine the total number of publications produced.
  
  
  RESULTS
  The median h index was 9 (range 0-68), with the 75th, 90th, and 95th percentiles being 17, 26, and 36, respectively. The h indices increased significantly with increasing academic rank, with the median for instructors, assistant professors, associate professors, and professors being 2, 5, 10, and 19, respectively (p < 0.0001, Kruskal-Wallis; all groups significantly different from each other except the difference between instructor and assistant professor [Conover]). Departmental chairs had a median h index of 22 (range 3-55) and program directors a median of 17 (range 0-62). Plot of the log of the rank versus h index demonstrated a remarkable linear pattern (R(2) = 0.995, p < 0.0001), suggesting that this is a power-law relationship.
  
  
  CONCLUSIONS
  A survey of the h index for all of academic neurosurgery is presented. Results can be used for benchmark purposes. The distribution of the h index within an academic population is described for the first time and appears related to the ubiquitous power-law distribution.
authors.affiliation: Department of Neurosurgery, Allegheny General Hospital, Pittsburgh, Pennsylvania 15212, USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Spearman
authors.forename: Madeline J
authors.initials: MJ
authors.lastname: Quigley
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Quigley
authors.forename: Jack E
authors.initials: JE
authors.lastname: Wilberger
mesh_terms: D015706:Bibliometrics; D009493:Neurosurgery / Q000706:statistics & numerical data*; D011642:Publications / Q000706:statistics & numerical data*