|Year : 2018 | Volume
| Issue : 3 | Page : 87-88
H-Index and the other metrics in analyzing Authors' impact
Editor-in-Chief, Department of Plastic, Reconstructive, Aesthetic and Hand Surgery, Faculty of Medicine, Dokuz Eylul University, Izmir, Turkey
|Date of Web Publication||2-Jul-2018|
Department of Plastic, Reconstructive, Aesthetic and Hand Surgery, Faculty of Medicine, Dokuz Eylul University, Izmir
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
CenkD. H-Index and the other metrics in analyzing Authors' impact
. Turk J Plast Surg 2018;26:87-8
The increase in the number of scientific articles brought up the problem of evaluating authors' metrics. The number of publications, the number of citations to the publications, and impact factors of the journals are the most commonly used parameters. However, extracting and validating these data are extremely important in obtaining objective results.
The h-index was first introduced in 2005 by Hirsch to calculate an author's scientific research achievement.  It is based on the number of an author's individual publications and the number of citations that these publications have attracted. Because it is very easy to understand and calculate the h-index, it gained popularity among various scientific tools, such as Web of Science, Scopus, and Google Scholar. It is defined as h and equals the number of publications that have received at least h citations. For example, an author's h-index is 8, if he/she has at least 8 publications that each has received at least 8 citations. The correlation between citations and the number of publications is shown in [Figure 1].
|Figure 1: The correlation between citations and the number of publications|
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In order to understand the calculation of h-index, examples of h-index for different authors are given in [Table 1].
|Table 1: The calculation of h-indices for three different authors, each having 11 publications with different number of citations |
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The number of total citations of Author C's publications is 147, which is much lower than Author's B's citations. But still, Author C has a higher h-index, compare to Author B. Author B is mostly concentrated on the first 4 publications, and the rest of his/her publications have attracted much less citations. On the other hand, Author C had more consistent citations for his/her publications. The h-index of Author A will raise to 9, as soon as he receives the 9 th citation for his publication 9.
Due to these disadvantages of the h-index, more author evaluation metrics have been proposed. Bornmann et al. published a meta-analysis of h-index and its variants.  All these variants seek better objective outputs; however, their additional parametric inputs lose their simplicity. The Hirsch-type indices, such as g-index, h(2)-index, a-index, r-index, ar-index, m quotient, m-index, hw-index, hm-index basically reflect either the productivity of an author or the impact of a publication. , Some of the other metrics for author impacts have been discussed below.
In 2006, a year after h-index has been defined, Egghe proposed the g-index giving additional credits for the highly cited articles. 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 on average at least g citations. 
Age-weighted citation rate
The number of citations for a publication is divided by the year since it has been published. New and less cited publications that have no contribution to the h-index increase age-weighted citation rate (AWCR). 
The AW-index is defined as the square root of the AWCR to allow comparison with the h-index; it approximates the h-index if the (average) citation rate remains more or less constant over the years. 
The Eigenfactor score
The Eigenfactor score has been developed as an academic research project of Bergstrom et al., in 2008. It is correlated with the journal impact factor. Citations in a high impact factor journals get more credits than the journals with lower impact factor. 
The e-index takes into account the highly cited articles of an author which is ignored in h-index. It helps to discriminate the authors with the same h-index. 
If w of an author's publications has at least 10 w citations each and the other publications have fewer than 10 (w+1) citations, his/her w-index is w. This also implies that one has not achieved the higher level: w+1 of his/her papers have at least 10 (w+1) citations each. 
Author impact factor
Author impact factor (AIF), which is similar to the journal impact factor. The AIF of an Author A in year t is the average number of citations given by papers published in year t to papers published by A in a period of Δt years before year t. AIF is correlated with the scientific productivity of an author for a certain period. 
The most common components of these indices are the number of publications, the number of citations, average number of citations per paper, average number of citations per author, average number of papers per author, the age of the publication, and journal impact factors. Since every index uses a different combination of these components, author citation metrics may differ significantly. To choose the best index, one should consider the basic fact that lies beneath in determining these indices.
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Bornmann L, Mutz R, Hug SE, Daniel HD. A multilevel meta-analysis of studies reporting correlations between the h index and 37 different h index variants. J Informetr 2011;5:346-59.
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