LAUSR

The ‘Hirsch index’ or the h-index is a leading author-level research metric, and its value denotes the ‘h’ number of papers having at least an ‘h’ number of citations. One of the major drawbacks of the h-index is the lack of sensitivity it demonstrates to highly cited papers beyond the ‘h’ value. What does this mean? Let us suppose a researcher has an h-index of 31. An article of this researcher has already received 31 citations and has achieved a ‘h top class’ or ‘Hirsch-core’. It does not matter for the h-index if this article gets continuously cited more and whether it receives 100 or 300 more citations. Hence, the h-index is insensitive to the highly cited work. To get a better measure of a set of articles’ global citation performance, the ‘g-index’ was introduced by Leo Egghe in 2006 as an improvement over the h-index. The g-index is defined as ‘the largest number such that the top ‘g’ articles received together at least g citations. The citations are considered in a descending order. For example, let us suppose a researcher has 4 publications with citations in descending order as 4,3,3,0. The g-index would be 3, since the sum of the first three citations is >9 but the sum of all four citations is not >16. The unique advantage of the g-index is that it considers highly cited papers beyond the ‘h-value’ or the ‘Hirsch core’. Hence, more weight is allotted to highly cited papers. The g-index retains the advantages and overcomes the disadvantages of the h-index. The g-index is also very helpful for comparing researchers with identical ‘h-index’, who may be competing for limited resources. It has also been used to assess the academic productivity of oncology residents and practicing neurosurgeons. The ‘g-index’ of a researcher is always higher than the ‘h-index’. Using the Harzing publish or perish website (https://harzing.com/resources/publish-or-perish), researchers can utilize data from the google scholar or citation databases to measure their ‘g-index’. Similar to the g-index, the e-index, proposed by Chun-Ting Zhang in 2009, also considers the underestimation of the citations by the ‘h-index’, and focuses on the highly cited papers. It also helps in better evaluation of researchers with different total citations but similar ‘h-index’. The e-index is a complementary metric to the h-index in assessing highly cited researchers, where even a g-index may not be able to catch the loss of citation data. The e-index helps assess the ignored excess citations that they may be receiving over and above the h-index. However, e-index is not a good tool to use for researchers with few publications or citations. Evaluating the h-index alone would be an incorrect measure of research assessment, especially for highly cited researchers. A combination of the h-index, g-index, and the e-index gives a better measure of the global citation performance and individual research impact.