title: Part II: Should the h-index be modified? An analysis of the m-quotient, contemporary h-index, authorship value, and impact factor.
abstract: OBJECTIVE
  The widely accepted h-index depends on the citation analysis source and does not consider the authorship position, the journal's impact factor (IF), or the age of the paper or author. We investigated these factors in citation statistics of academic neurosurgeons.
  
  
  METHODS
  An uncorrected h-index and the m-quotient, which corrects for career length, were calculated by the use of Scopus and Google Scholar. In a subset of neurosurgeons, we computed the contemporary h-index (hc), which accounts for the age of the publications; the authorship value (AV), weighted by author position; and the journal IF. An "overall' average for AV and IF including most of an author's publications and an average for publications comprising the h-index ("h-index core") were calculated.
  
  
  RESULTS
  When we used Google Scholar, the mean h-index was significantly greater than that calculated when we used Scopus (P = 0.0030). m-quotient and hc-index increased with academic rank, with an m-quotient >1 achieved by 69% of chairmen and 48% of professors. The effect of AV was greatest on the greater h-indices. The average IF for the h-index core was greater than the overall IF, which did not correlate with academic rank. Few neurosurgeons consistently publish in high-impact journals.
  
  
  CONCLUSIONS
  Google Scholar tends to inflate the h-index. The m-quotient and hc-index allow comparisons of researchers across time. Although average journal IF did not differ significantly among neurosurgeons academic ranks, it should be noted for individuals who consistently publish in high-impact journals. We recommend the creation of individual bibliometric profiles to better compare the academic productivity of neurosurgeons.
authors.affiliation: University of Tennessee Health Science Center, Memphis, Tennessee, USA.
authors.forename: Nickalus R
authors.initials: NR
authors.lastname: Khan
authors.forename: Clinton J
authors.initials: CJ
authors.lastname: Thompson
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Taylor
authors.forename: Kyle S
authors.initials: KS
authors.lastname: Gabrick
authors.forename: Asim F
authors.initials: AF
authors.lastname: Choudhri
authors.forename: Frederick R
authors.initials: FR
authors.lastname: Boop
authors.forename: Paul
authors.initials: P
authors.lastname: Klimo
mesh_terms: D000367:Age Factors; D001319:Authorship; D015706:Bibliometrics; D003627:Data Interpretation, Statistical; D006801:Humans; D020407:Internet; D055811:Journal Impact Factor; D009493:Neurosurgery / Q000592:standards* / Q000706:statistics & numerical data; D010506:Periodicals as Topic; D011643:Publishing; D064878:Web Browser
keywords: AV; Authorship; Authorship value; Bibliometrics; Contemporary h-index; Google scholar; Impact factor; Neurosurgery; Scopus; h-index; hc; m-quotient