The G-index was proposed by Leo Egghe in his paper "Theory and Practice of the G-Index" in 2006 as an improvement on the H-Index.  

G-Index is calculated this way: "[Given a set of articles] ranked in decreasing order of the number of citations that they received, the G-Index is the (unique) largest number such that the top g articles received (together) at least g^2 citations." (from Harzig's Publish or Perish Manual)

Advantages of the G-Index:

  • Accounts for the performance of author's top articles
  • Helps to make more apparent the difference between authors' respective impacts.  The inflated values of the G-Index help to give credit to lowly-cited or non-cited papers while giving credit for highly-cited papers.  

Disadvantages of the G-Index:

  • Introduced in 2006. and debate continues whether G-Index is superior to H-Index.  Might not be as widely accepted as H-Index.