New insights into the relationship between the h-index and self-citations?

Sir, Within the last decades, the increase in the number of researchers in the scientific community has led to an increase in the number of funding and tenure decisions that have to be made. It is therefore a necessity to find simple yet objective measures to compare the scientific achievement of researchers. Hirsch’s h (2005) has been claimed to have these attributes because it incorporates both quantity and impact of a researcher’s publications. One of the positive attributes of the h-index, compared to other citation-based scientometric measures, is that it is quite robust against self-citation behavior (Engqvist & Frommen, 2008; Hirsch, 2005). However, a recent article by Gianoli andMolina-Montenegro (2009) cast the truth of this opinion into doubt. Gianoli and Molina-Montenegro’s critique was twofold: First, they stated that an author’s self-citation behavior does have an impact on the h-index. Second, this effect seems more pronounced for authors with a low h. The first result of Gianoli and Molina-Montenegro study is very much the same as found in a previous analysis (Engqvist & Frommen, 2008); however, the interpretation differed. Engqvist and Frommen looked at the effect size and showed that even excessive self-citation will cause the h-indices of two, in other respects, equivalent scientists to differ only slightly, on average merely by one unit. Any citation-based measure will be affected by self-citations, but Engqvist and Frommen’s analysis shows that the h-index is remarkably robust. Gianoli and Molina-Montenegro in contrast did not quantify the effect self-citations have on an author’s h-index, but concluded that self-citations do have a great impact on the h-index. The novel part of Gianoli and Molina-Montenegro’s contribution is the finding that the h-index might be more sensitive to self-citations for authors with a low h-index (i.e., authors at an early career stage). However, we identified three major errors in their analysis, which also highlight the pitfalls one might encounter in the analysis of self-citation effects. First, the authorsmakeuse ofWebofScience’s “viewwithout self-citations” option. Unfortunately, this function does not provide the number of citations without self citations,