# Metrics

Note: This tutorial was originally written for Publish or Perish version 4 and all screenshots come from this version. However, the information as such is also applicable for the latest Publish or Perish version 5.

Although most bibliometric analyses tend to focus on fairly complex metrics such as the h-index and its variations, there is a lot one can learn from relatively simple metrics included in Publish or Perish.

## Metrics related to papers, citations and academic age

Here we look at the number of papers, citations, and the number of years since the academic’s first publication, in combination with the number of authors per paper.

• Citations per paper = total citations/total papers
• Citations per year = total citations/years since first paper
• Citations per author = divide citations for each publication by the number of authors and sum the resulting citations; this is the single-authored equivalent number of citations for the author in question.
• Papers per author = divide each publication by the number of authors and sum the fractional author counts; this is the single-authored equivalent number of papers for the author in question.
• Authors per paper = add up the total number of authors involved in the publications for the author in question and divide this by the number of papers. [Please note: Single publications with a large number of authors can increase this metric substantially. Hence, it is not as good a reflection of an author’s individual productivity as the number of papers per author.]

## What can we learn from simple metrics?

The screenshots below compare my own publication record (left) with that of a former colleague at the University of Melbourne, Maria Kraimer (right), now Professor at the University of Iowa. For both I have merged duplicate publications.

I chose Maria because her total number of citations (app. 8300) and time since first publication (17 years) are quite similar to mine (app. 9500 and 20 years). As a result, our number of citations per year is very similar (475 vs 488).

## Different publication strategies

However, it is clear that we have followed different publication strategies. I have published more than 2.5 times as many papers (111 vs. 41). An important reason is that she has focused mainly on publications in top US journals, whilst I have published in a wider range of journals.

I have also published books and book chapters as well as white papers and other research products (such as Publish or Perish and the Journal Quality List) that attract citations. As a result the number of citations per paper is much higher for Maria (202.54) than for me (85.56). This could be seen as evidence of publishing higher quality papers.

## Differences in co-authorship patterns

However, Maria has also published with a much larger number of co-authors. As a result, my number of “single-authored” citations (cites/author) is 2.5 times as high as hers. The difference in the number of single-authored equivalent papers is even larger, with my record showing more than 5 times as many single-authored equivalents (73 papers vs. 14 papers).

This is also reflected in the average number of authors per paper. For Maria the mean is 3.17, whereas for me it is 1.86. This difference is not as large as one might expect from the other metrics, but single papers with many co-authors can heavily influence this metric. Publish or Perish therefore also provides the mode for this metric. For Maria the mode is 3, whereas for me the mode is 1 (i.e. single-authored).

## Conclusion

Neither of these two publication strategies is inherently better than the other. They just reflect different approaches to publishing, which might be shaped by factors such as type and country of doctoral training, country of employment, research area, and personal temperaments.

The variety of metrics provided by Publish or Perish allows one to select the metrics most appropriate to one’s purpose. However, there are metrics that are designed to combine both productivity (number of papers) and impact (number of citations). The h-index, to be discussed next, is the most important of these metrics.

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