Journal Evaluation & Measuring Author Impact

Citation count measures the impact of an author by: counting the total number of times an author's work has been cited by other articles.

Both Scopus and Google Scholar include overall author citation counts in their author profiles. However, these numbers will likely be different in each database due to differences in the content of each index.

Citation counts can best compare authors in the same discipline at the same general point in their careers. Authors who have been writing for longer will tend to have more citations, and different disciplines have varying citation practices, some citing much more or much less than others. When using this metric, it is also important to remember that while publications with more citations may "on average" have more impact, the impact of an individual publication may vary. Citation counts are not always a simple measure of quality or impact. See the Article Metrics section for more information.

Measures the intersection of an author's productivity and impact using both the total number of publications produced by an author and the total number of citations to each of those works. 

More formally, the h-index is:

the number of published papers (h) that have received at least (h) citations.

For example, an author has an h-index of 4 when they have published 4 papers that have received at least 4 citations each. It is an easy to calculate metric that favors authors who have published many articles that all have a high citation count. Just as with a simple citation count, the h-index is most useful to compare the impact of authors within the same discipline, as different areas of study have different citation practices.

The h-index has been criticized for not taking the role of the author into account, undervaluing highly cited papers in general, and failing to recognize authors who have published a few very highly cited papers. It is also not seen as a great measure for early career researchers to use, as it takes time for articles to be cited in the literature, meaning that more experienced researchers' scores tend to be higher.

Calculating the h-index: While the h-index can be calculated manually using the approach pictured above, both Scopus & Google Scholar will calculate the h-index automatically on their author profiles. Authors should make sure their citations in each database are up to date and that all articles have been claimed under one author profile. Differences in author-publication data will affect the final h-index calculation, and each citation database may return a different h-index as a result.

An alternative to the h-index, the g-index attempts to compensate for a known issue with the h-index. It does this by giving more weight to highly cited papers so that authors with a few highly cited papers, get more credit for their work than they would with the h-index measure. 

The free online tool Publish or Perish will automatically calculate the g-index for an author, along with the other author metrics mentioned above. It uses data from both Scopus & Google Scholar. 

This metric is only used by Google Scholar and can be found on their author profile tool. Simply put, it is the number of articles published by an author that have received at least 10 citations.