16.3.3 Individual h-index

The Hi-norm corrects for the number of co-authors. I use the Publish or Perish alternative rather than the Batista et al. (2006) option. The latter divides the standard h-index by the average number of authors in the articles that contribute to the h-index.

The PoP alternative first normalizes the number of citations for each paper by dividing the number of citations by the number of authors for that paper, then calculates the h-index of the normalized citation counts. This approach is much more fine-grained than Batista et al.'s; I believe that it more accurately accounts for any co-authorship effects that might be present and that it is a better approximation of the per-author impact, which is what the original h-index set out to provide.

We have seen above that the number of co-authors in the Sciences is generally larger than the number of co-authors in the Social Sciences and Humanities. Hence, we would expect differences between disciplines to be smaller for the individual h-index than for the general h-index. Figure 10 shows that this is indeed the case.

Figure 10: H-index compared with the Individual h-index for different disciplines

At 28 the average h-index in the Sciences is one third higher than the average h-index in the Social Sciences and Humanities at 21. However, the average Hi-norm for the two groups is virtually identical: 17 for the Sciences and 18 for the Social Sciences and Humanities.