Author Impact Metrics: H-Index, G-Index, and i10-Index Explained

Author Impact Author Impact H-index Explained College of Medicine Al Nahrain University 2017

Measures of Author Impact Measures of Author Impact An author's impact on their field or discipline has traditionally been measured using the number of times their academic publications are cited by other researchers. There are numerous algorithms that account for such things as the recency of the publication, or poorly or highly cited papers. While citation metrics may reflect the impact of research in a field, there are many potential biases with these measurements and they should be used with care. For a critique of author impact factors . H-Index The most widely used research metric, measures both productivity and impact of an author's scholarly output. Tools for calculating your H-index include Web of Science and Google Scholar. G-Index Proposed in 2006 by Leo Egghe as an alternative to the H-index, adds more weight to highly cited articles. i10-Index A very simple measure of impact, this metric is only used by Google Scholar.

H H- -Index Index The H-Index is used to quantify research output by measuring author productivity and impact. H-Index = number of papers (h) with a citation number h. Example: a scientist with an H-Index of 37 has 37 papers cited at least 37 times. Advantages of the H-Index: Allows for direct comparisons within disciplines Measures quantity and impact by a single value. Disadvantages of the H-Index: Does not give an accurate measure for early-career researchers Calculated by using only articles that are indexed in google scholar . If a researcher publishes an article in a journal that is not indexed by Web of Science, the article as well as any citations to it will not be included in the H-Index calculation. Tools for measuring H-Index: Web of Science Google Scholar

G G- -Index Index 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.

i10-index Created by Google Scholar and used in Google's My Citations feature. i10-Index = the number of publications with at least 10 citations. This very simple measure is only used by Google Scholar, and is another way to help gauge the productivity of a scholar. Advantages of i10-Index Very simple and straightforward to calculate My Citations in Google Scholar is free and easy to use Disadvantages of i10-Index Used only in Google Scholar Here is a screenshot of a Google Scholar My Citations page for Charles Darwin (you can see the i10-Index highlighted in the small table):

What is the h index? The h index was proposed by J.E. Hirsch in 2005 and published in the Proceedings of the National Academy of Sciences of the United States of America. The h index is a quantitative metric based on analysis of publication data using publications and citations to provide an estimate of the importance, significance, and broad impact of a scientist s cumulative research contributions. According to Hirsch, the h index is defined as: A scientist has index h if h of his or her Np papers have at least h citations each and the other (Np h) papers have h citations each.

How Calculated How Calculated: Number of papers (h) that have received at least h citations. As an example, an h index of 10 means that among all publications by one author, 10 of these publications have received at least 10 citations each. Hirsch argues that the h index is preferable to other single-number criteria, such as the total number of papers, the total number of citations and citations per paper. However, Hirsch includes several caveats: A single number can never give more than a rough approximation to an individual s multifaceted profile; Other factors should be considered in combination in evaluating an individual; There will be differences in typical h values in different fields, determined in part by the average number of references in a paper in the field, the average number of papers produced by each scientist in the field, and the size (number of scientists) of the field; and For an author with a relatively low h that has a few seminal papers with extraordinarily high citation counts, the h index will not fully reflect that scientist s accomplishments.

Resources to Find the h index Resources to Find the h index Google Scholar Google Scholar provides the h index for authors who have created a profile. Publish or Perish Publish or Perish is a software program that retrieves and analyzes academic citations from Google Scholar and provides the h index among other metrics. Publish or Perish is handy for obtaining the h index for authors who do not have a Google Scholar profile. Scopus Scopus provides a Citation Tracker feature that allows for generation of a Citation Overview chart to generate a h index for publications and citations from 1970 to current. The feature also allows for removal of self-citations from the overall citation counts. Web of Science Web of Science allows for generation of the h index for publications and citations from 1970 to current using the "Create Citation Report" feature.

Strengths of the Strengths of the h h index index The h index is a metric for evaluating the cumulative impact of an author s scholarly output and performance; measures quantity with quality by comparing publications to citations. The h index corrects for the disproportionate weight of highly cited publications or publications that have not yet been cited. Several resources automatically calculate the h index as part of citation reports for authors.

Shortcomings of the Shortcomings of the h h index index The h index is a metric to assess the entire body of scholarly output by an author; not intended for a specific timeframe. The h index is insensitive to publications that are rarely cited such as meeting abstracts and to publications that are frequently cited such as reviews. Author name variant issues and multiple versions of the same work pose challenges in establishing accurate citation data for a specific author. The h index does not provide the context of the citations. The h index is not considered a universal metric as it is difficult to compare authors of different seniority or disciplines. Young investigators are at a disadvantage and academic disciplines vary in the average number of publications, references and citations. Self-citations or gratuitous citations among colleagues can skew the h index. The h index will vary among resources depending on the publication data that is included in the calculation of the index. The h index disregards author ranking and co-author characteristics on publications. There are instances of paradoxical situations for authors who have the same number of publications, with varying citation counts, but have the same h index. As an example, Author A has eight publications which have been cited a total of 338 times and Author B also has eight publications which have been cited a total of 28 times. Author A and Author B have the same h index of 5 but Author A has a higher citation rate than Author B. See Balaban, AT. 2012. Positive and negative aspects of citation indices and journal impact factors. Scientometrics. DOI: 10.1007/s11192-102-0637-5