Abstract
Hirsch’s h-index cannot be used to compare academics that work in different disciplines or are at different career stages. Therefore, a metric that corrects for these differences would provide information that the h-index and its many current refinements cannot deliver. This article introduces such a metric, namely the hI,annual (or hIa for short). The hIa-index represents the average annual increase in the individual h-index. Using a sample of 146 academics working in five major disciplines and representing a wide variety of career lengths, we demonstrate that this metric attenuates h-index differences attributable to disciplinary background and career length. It is also easy to calculate with readily available data from all major bibliometric databases, such as Thomson Reuters Web of Knowledge, Scopus and Google Scholar. Finally, as the metric represents the average number of single-author-equivalent “impactful” articles that an academic has published per year, it also allows an intuitive interpretation. Although just like any other metric, the hIa-index should never be used as the sole criterion to evaluate academics, we argue that it provides a more reliable comparison between academics than currently available metrics.
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Notes
Academic age could be adjusted if a first publication occurred years before a steady stream of research output materialised, as might the case for a published conference paper or a book review.
We also collected data for Google Scholar and the Web of Science (ISI); the results for these databases were very similar in terms of the hIa-index’s attenuation of differences between disciplines and career length. The average hIa-index was very similar in Scopus and ISI, but was approximately 30–35 % higher in Google Scholar.
Two professors in Law and Physics had to be removed from the final sample as their publication patterns were very uncharacteristic of their field.
For instance, Veterinary Sciences, Land and Environment, and Earth Sciences could have been classified into a separate major discipline of Environmental Sciences. However, their h, hIA and author per paper metrics were very similar to the Sciences; hence they were merged into the Sciences category. Architecture, Building and Planning displays similarities with Engineering, the Social Sciences and the Humanities. However, our selected academics were all in the Architecture/Design field, which is more aligned with the Humanities tradition; hence they were classified into the Humanities cluster.
Apart from sample idiosyncrasies, this may have been caused by three factors. First, academics in the (Life) Sciences normally start publishing during their PhD, whereas this is less common for academics in other disciplines. Second, academics in the (Life) Sciences often have a longer career trajectory, with most academics taking on one or more postdocs before appointment as assistant professor. Finally, in Engineering, the Social Sciences and Humanities, academics might well have early career publications in outlets not included in Scopus, such as books or conference proceedings, or in journals not currently included in Scopus.
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Harzing, AW., Alakangas, S. & Adams, D. hIa: an individual annual h-index to accommodate disciplinary and career length differences. Scientometrics 99, 811–821 (2014). https://doi.org/10.1007/s11192-013-1208-0
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DOI: https://doi.org/10.1007/s11192-013-1208-0