Research Impact Metrics: Author Impact

The most commonly cited author-level impact factor. The h-index was developed in 2005 by Jorge Hirsch, a physicist at the University of California in San Diego. Hirsch's paper was published in Proceedings of the National Academy of Science (PNAS).

In that paper he states: "A scientist has index h if h of his/her Np papers have at least h citations each, and the other (Np − h) papers have no more than h citations each."

The validity of the h-index, however, has been called into question.

Many alternatives to the h-index are available and are becoming more and more prevalent. They include:

• Contemporary h-index
• Scholarometer
• Eigenfactor
• Egghe's g-index
• Zhang's e-index
• Google's l10-index
• Individual h-index
• R-impact
• Universal h-index
• w-index or Wu Index

Publish or Perish is a software program that retrieves and analyzes academic citations. It uses Google Scholar and Microsoft Academic Search to obtain the raw citations, then analyzes these and presents the following statistics:

• Total number of papers
• Total number of citations
• Average number of citations per paper
• Average number of citations per author
• Average number of papers per author
• Average number of citations per year
• Hirsch's h-index and related parameters
• Egghe's g-index
• The contemporary h-index
• The age-weighted citation rate
• Two variations of individual h-indices
• An analysis of the number of authors per paper.

It used to be that only the ISI Citation Indexes would list citing articles. That has changed, thanks to the linking abilities of the Web. Many databases will tell you that article X has been cited N times by articles in its database. Be aware that this number is based only on the articles indexed by that database; there may be other journals that cite your article that aren't listed in that database. So always check more than one database.

Below is a list of databases UK has subscriptions to that can serve as a starting place.

The database and search engine below have features to calculate h-index:

There is an international initiative that addresses problems arising from identifying researchers with similar or the same name.  It is ORCID, which issues unique identifiers to distinguish individual researchers. 

Below is the recording of a presentation about ORCID.  Click here for the presentation slides. 

Each citation source produces slightly different results depending on the content and coverage of the source. This underscores the importance of using multiple citation sources to judge the true impact of an author's work. The search strategy should be broad and inclusive enough to accommodate the following pitfalls.

• Search results vary by database used.
  
  
• Search all permutations of the cited author's name: last name; last name, first and middle initials; last name and first initial.
  
  
• Use an author disambiguation tool
  
  
• If someone is second or third author, search by the lead authors to locate the cited reference.
  
  
• Author names and titles in foreign languages and non-Roman script may require extra effort to determine their transcription or transliteration in each database.
  

Properly identifying authors and their papers is difficult for obvious reasons. How many articles are authored by J. Smith, Y. Lee, or L. Jackson? The groups below are working to solve this problem.

• ORCID - Open Researcher & Contributor ID
• ISNI - International Standard Name Identifier
• VIAF - Virtual International Authority File
• ResearcherID
• arXiv Author ID

ORCID is an international initiative that helps researchers disambiguate their identity.  You can receive your ORCID ID for free by visiting this page.  Here is some more information about ORCID.

• ORCID: A System to Uniquely Identify Researchers
• Open Researcher & Contributor ID (ORCID): Solving the Name Ambiguity Problem
• ORCID Open Source and Technical Community