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Journal of Postgraduate Medicine, Vol. 57, No. 3, July-September, 2011, pp. 264-265 Letter How honest is the h-index in measuring individual research output? BK Patro, AK Aggarwal Department of Community Medicine, School of Public Health, PGIMER, Chandigarh, India Code Number: jp11078 PMID: 21941081 Sir, Measuring the impact of the research output of an institution / individual is an important issue. It helps in the evaluation and comparison of the research output of institutions as well as individual researchers. Any research study is said to have achieved its purpose when its results are translated into policy, which further rolls out as a change in the program or practice guidelines. However, these changes usually follow the cumulative effect of multiple research studies, thus making it difficult to ascribe the credit to an individual researcher. Several bibliometric indicators have been developed to measure the output of research studies or publications, of which a number of publications and publications in high impact factor journals are the most popular ones. The number of publications is limited in its ability as an indicator of research output, as it speaks only about the volume of research, ignoring the quality. Publication in a high impact factor journal certainly points to the quality of the research study, but the impact factor is assigned to the journal as a whole rather than to the individual research publication. The impact factor of a journal is the average number of citations received per article published in that journal, during the two preceding years. A journal′s impact factor is based on two elements: the numerator, which is the number of citations in the current year compared to items published in the previous two years, and the denominator, which is the number of substantive articles and reviews published in the same two years. Substantive articles usually include articles, reviews, proceedings, or notes but not editorials or letters-to-the-editor. [1] The impact factor of journals remains to be a contentious issue and has drawn criticisms from the scientific community regarding its use to evaluate research studies. [2] It can be manipulated by changing editorial policies such as increasing the number of review articles or reducing the number of original articles, ahead of print publication (online first) or by encouraging authors for self citation. A summary of the commonly used bibliographic indicators are presented in [Table - 1]. The h-index was proposed in the year 2005, by J.E. Hirsch, to overcome the shortcomings of the Impact Factor in evaluating the impact of an individual researcher′s research output. The h-index attempts to measure both the volume and impact of the published study of a scientist or scholar. Index h, is defined as the number of articles with ≥ h citations. A researcher has an index h if the h of his or her N p articles have been cited at least h number of times and the remaining (N p - h) articless have been cited ≤ h times. An h-index of 10 translates to 10 research publications of a researcher having been cited at least 10 times. The h-index grows as the citations accumulate over a period of time, and thus, it depends on the ′academic age′ of a researcher. [3] Hirsch originally suggested for faculty of research universities that h ~ 12 might be a typical value for advancement to associate professor, and h ~ 18 might be typical value for advancement to full professor. The h-index can be manually calculated using citation databases. Subscription base databases, such as, Scopus and Web of Knowledge, provide automatic calculation of the h-index. Each database is likely to produce a different h value for the same researcher owing to different subscriptions (coverage of journals). Google scholar also provides a h value, which happens to be on the higher side than that of Scopus and Web of Knowledge. The h-index has its own pie of limitations and criticisms. One of the major limitations of the h index is its insensitiveness to the small number studies, which are highly cited. Similarly, it does not take account of the large number articles, which have less than h citations. As the h-index is dependent on the number of publications, a junior researcher with a relatively short research career is likely to have a disappointingly low h-index despite his innovations. The h-index also does not account for the positioning of the researchers in the list of authors. [4] The limitations of the h-index have been addressed by new bibliometric indicators such as the m and h core index. Despite its limitations it is being used to evaluate researchers for career advancement in universities and medical schools across the globe. The h-index seems to be a promising index for measuring the scientific output of a researchers, but should not be used in isolation. In addition, other measures of research output measures such as innovations and societal impact should also be considered in measuring the scientific output of a researcher. References
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