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The most common number of authors in a scientific article is 2–4 authors, according to a 2009–2018 survey based on Web of Science publication records. There were ten or fewer authors in almost 95% of the articles. However, a scientific article can have a significant number of authors – especially in fields where research is carried out in large research groups or where extensive cooperation is otherwise required, e.g. in funding research infrastructures or acquiring data. In recent years, there has been an increase in hyper authorship, i.e. articles with more than 100 authors. In particular, the proportion of articles by with more than 1,000 authors has increased, although it still remains small overall. (Adams et al., 2019).
As the high number of authors may influence the number of citations the publication receives (especially when the authors come from different countries), there is a risk that hyper authorship articles may distort the results of analyses. This should be taken into account when analysing results, at the very least. The distorting effects can be mitigated by fractionalising, which reduces the significance of publications in the overall context, and by using Top x% indicators, which are less sensitive to the influence of publications that have received very high numbers of citations. Indicators to normalise the number of background countries are also being developed for some analysis tools (InCites Collab-CNCI). If distorting effects are observed, one solution is to exclude articles by more than 100 authors from organisational and country-level analyses (Adams et al., 2019). However, this is not explicitly recommended, as these publications belong to the subject under evaluation. The typical number of authors varies by the field of science, and in some fields hyper authorship articles are very common and are part of a normal publishing practice. If it is decided to exclude publications on the basis of the number of authors, this can be done by using the filters in the analysis tools (InCites and SciVal).
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