Author-level metrics, such as the h-index, and journal-level metrics, such as the impact factor, are standard tools that are used in bibliometric analyses. Other approaches, for example altmetrics and analyzing activity in professional academic networks, play different roles in evaluating the impact of scientific work within a discipline. All metrics have limitations and should not be used as the sole source for assessment and evaluation.
Author Level Metrics
Publication and citation counts have traditionally been used to measure the research impact of an author’s work. Various author-level metrics based on citation analysis have been developed in recent years.
The most widely used is the h-index, which measures the productivity and impact of an author’s work. It states that “h” number of publications have been cited at least “h” times. Web of Science, Scopus, Google Scholar, and other databases can be used to calculate the h-index; however, as each of these databases has a different data source, the calculated h-index values will vary between databases. Further, the h-index will also vary with the date of calculation.
Other metrics, such as the g-index, Google Scholar’s i10 index, and the hI,annual index have been developed to address some of the criticisms of the h-index.
Authors can proactively work to make certain that all of their publications and citations are counted in the calculation of these indexes by creating unique author identification profiles using tools such as ORCID, ResearcherID, or Google Scholar Citations. The Scopus Author ID, which is automatically generated for every author, helps to ensure that the correct publications are assigned to the correct person within the Scopus database. Authors can use the Scopus Author Feedback Wizard to submit any necessary changes.
Journal Level Metrics
Journal-level metrics attempt to measure the reputation of individual journals. The most widely known and oldest of these indicators is the impact factor, which is used to rank the journals included in the Web of Science database. The impact factor is a comparison of the number of citations and the number of articles recently published within a journal. Impact factors are available through the database Journal Citation Reports.
Alternate journal-level measures include the Scimago Journal Rank, which uses citation data included in the Scopus database, and Eigenfactor, which uses data from the Web of Science.
Altmetrics (from “alternative metrics”) are measures of online activity, which are gathered from social media or other online tools. Examples of these alternative forms of metrics range from the number of downloads or views that an article receives to the number of times it has been bookmarked in Mendeley or tweeted about. These metrics, which can be used for authors, institutions, journals, or articles are in their beta stage and are still being developed, although you can see an example of how the Public Library of Science (PLoS) is teaming up with the company Altmetric to use this type of information.