All about metrics
There are several metrics commonly used to measure an author’s research impact. For example:
h-index: this is the most commonly used index to measure a researcher’s productivity (number of publications) and impact (citations).
Citation counts: the number of times a scholarly work (such as an article, book, or conference paper) has been cited by other researchers in their own publications.
Impact factor: a metrics reflecting the yearly average number of citations to recent articles published in an academic journal. It is often used as an indicator of the journal’s relative importance within its field, with higher impact factors signifying greater influence.
G-index: This index gives more weight to highly cited articles, offering a more nuanced view of a researcher’s impact, especially if they have a few very highly cited papers.
i10-index: This is the number of publications with at least 10 citations. It’s a simpler metric that can be useful for comparing researchers with shorter careers
M-quotient: This metric divides the h-index by the number of years the researcher has been active, providing a rate of impactful work over time.
It is worth noting that impact extends beyond metrics, and qualitative assessments are also valuable in evaluating research impact.
h-index
The h-index was suggested in 2005 by physicist Jorge E. Hirsch at UC San Diego.
[Hirsch, J. (2005) An index to quantify an individual’s scientific research output. PNAS 102(46):16569–72]
Essentially, it is an index to measure:
- a researcher's cumulative research contributions
- both researcher's productivity (number of publications) and impact (citations).
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Where to find h-index
Why h-index varies?
Why does the same author have different h-index values across various databases?
Database Coverage: Each database has its own collection of scholarly works. Some databases include a wider range of publication types, such as books and conference papers, which can contribute to higher citation counts.
Citation Analysis Method: Different databases use different methods to track and count citations.
Update Frequency: Databases update their citation data at different frequencies. A database that updates more frequently may show a higher h-index due to more current citation information.
Self-Citation Policies: The way self-citations are treated can differ among databases. Some may exclude self-citations from the h-index calculation, while others may include them.
Time Span: The time span covered by the database can also affect the h-index. Older databases may show a higher h-index for an author due to a longer citation history.
Limitations of the h-index
- It does not take into account the number of authors on a paper.
- It penalizes early-career scientists. Outstanding scientists with only a few publications cannot have a high h-index, even if all of those publications are ground-breaking and highly cited.
- Review articles have a greater impact on the h-index than original papers since they are generally cited more often.
- h-index cannot be used to compare fields and scientific disciplines directly.