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Indicators

time, does yield a strong indicator of scientific performance. This idea changed
with the availability of the h-index which was precisely designed for the
evaluation of individual scientists. Let us now have a look at some advantages
and disadvantages of the h-index as an indicator for individuals. Such lists
were presented for example in Gla ¨nzel (2006) and Liu & Rousseau (2007).

7.3.2 Advantages and Disadvantages of the h-index

Advantages of the h-index
• It is a mathematically simple index.
• As it combines two types of activity (in the original setting this is cita-
tion impact and publications) it can be argued that it is a better index
than total number of publications or total number of citations alone.
• It encourages highly visible work.
• Increasing the number of publications alone does not have an immedi-
ate effect on this index.
• It is a robust indicator in the sense that small errors in data collection
have no or little effect (Rousseau, 2007a; Vanclay, 2007)—but see the
disambiguation problem in the next list.
• Single peaks (top publications) have no influence on the h-index.
• In principle, any document type can be included.
• In most cases publications that are hardly ever cited do not influence the
h-index (an exception occurring when the h-index itself is very low).
• As the h-index is time-dependent it can be used as an indicator to
study or evaluate a scientist’s career.
Moreover, the h-index can be applied to any level of aggregation.
This means that not only to scientists but also to different groups of scien-
tists, such as all scientists belonging to a research institute, belonging to a
university, or belonging to the same country. It can even be applied to
most source-item systems (see Section 9.3) such as books per library clas-
sification category and loans (Liu & Rousseau, 2007, 2009). The value
associated with a source such as an article, is in general referred to as its
magnitude value, e.g., the number of received citations.
Disadvantages of the h-index
Yet, it is well-known that the h-index has several disadvantages. Some
of these it shares with any other citation-based indicator.
• Like most citation measures it is field-dependent, database dependent,
and may be influenced by self-citations.
• Highly cited work is not necessarily high quality work.