Research Impact/Bibliometrics

This guide provides an introduction to using Web of Science, Scopus and other resources to determine journal impact, individual researcher impact, and article impact.

Finding Individual Research Impact

Researchers often want to know the impact of their individual articles or overall body of research. There are many different calculations that attempt to express an author's impact. This guide will discuss two of the most common methods: citation analysis and h-index.

Each impact metric has criticisms, and shouldn't be used as a sole measure of a researcher's success. Different fields have different citation patterns. This makes it difficult to compare researchers in different fields.

For a very detailed discussion of other metrics and how they compare, see:

Bornmann, L., Mutz. R, Hug, S.E., and Daniel,H. (2011)  A multilevel meta-analysis of studies reporting correlations between the h index and 37 different h index variants, Journal of Informetrics, 5(3), p. 346-359

 

Citation Analysis

Citation analysis consists of determining how many times a particular work or group of works has been cited by other authors. See the tabs on the left for information on how to find this in several databases.

In addition to Web of Science, Scopus, and Google Scholar, which are discussed on this guide in more detail, other databases provide some citation count information. These include JSTOR, PsycINFO, ERIC, Sociological Abstracts, PubMed, America History and Life, and Historical Abstracts.

Here is an example from PsycINFO:

Example of citation count for an article in PsycINFO

Remember that each database provides information on times the article has been cited by articles in other journals also indexed in that database. No database indexes the entire universe of journals. Therefore, each database will most likely give a different citation count. When using citation count (or any other metric), it is important to ask "what is the source of the data?"

H-Index

One of the most commonly used metrics to calculate an individual author's impact is the h-index. The h-index, created by researcher Jorge E. Hirsch, attempts to measure the total impact of a body of work, while controlling for very frequently cited or very infrequently cited papers. In order to calculate it, the papers are arranged in descending order of times cited. Then the h-index is determined by the number of papers in the list (h) that have h or more citations.

In other words, look in the chart for the highest-numbered article where the number of citations is greater than or equal to the article's number. That article number is the h-index.

This author’s total number of articles is 7 and total number of citations is 140. The author's h-index is 3, because there are 3 articles with 3 or more citations:

Article #

# of citations

1

120

2

10

3

4

4

2

5

2

6

2

7

0

This author, with the same total number of articles (7) and citations (140) as the author above, has an h-index of 7, because there are 7 articles with 7 or more citations

Article #

# of citations

1

20

2

20

3

20

4

20

5

20

6

20

7

20

 

H-index can be calculated for any group of articles for which citation data is available including:

  • all the work of an individual author
  • the work of a group of authors, or even an entire university
  • a journal as a whole

H-index can also be calculated for any time period; an entire career or a selected time span. 

See the tabs on the left for information about finding h-index in different databases. It is important to keep in mind that each database calculates the h-index based on citations from other journals also indexed in that database. No database indexes the entire universe of journals. Therefore, each database will most likely give a different h-index number. When using h-index (or any other metric), it is important to ask "what is the source of the data?"