Number of references: a large-scale study of interval ratios
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Number of references: a large-scale study of interval ratios Jeppe Nicolaisen1 · Tove Faber Frandsen2 Received: 31 March 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The paper presents a large-scale study (covering 26,998,764 items) of the development in the number of references over time (1996–2019) in three document types (articles; reviews; notes) from seven fields (Arts and Humanities; Social Sciences; Computer Science; Mathematics; Engineering; Medicine; Physics and Astronomy). Using interval ratios instead of average numbers, the paper makes it possible to follow the development, and to locate the main causes of growth in the number of references over time. The results show significant differences between fields and document types. The number of references in journal articles and reviews are growing in all fields (except for the reviews in Arts and Humanities that remain stable over time), but at different pace; The number of references in notes are growing in some fields (again at different pace) and are stable in others. The observed growth is primarily caused by a drop in short reference lists and a corresponding increase in a bit longer and medium size reference lists. Long and very long reference lists remain much more stable in shares over time, and does therefore not contribute much to the observed growth. The results underline the importance of normalizing citation data, and for taking citation inflation into account when conducting citation analyses expanding different fields, document types, and longer time-periods. Keywords Citing behavior · Document types · Number of references · Reference analysis · Subject areas · Normalization · Citation inflation
Introduction The development in number of references in scientific publications over time has been studied at least since 1965 when Derek J. de Solla Price reported that on average, journal papers contain 15 references. More specifically, he had found that about 10% of all papers contained no references whereas 5% contained more than 45 references. According to de Solla Price (1965), 85% of all papers contained 25 or fewer references. This is a quite * Jeppe Nicolaisen [email protected] 1
Department of Communication, University of Copenhagen, Njalsgade 76, 2300 Copenhagen S, Denmark
2
Department of Design and Communication, University of Southern Denmark, Universitetsparken 1, 6000 Kolding, Denmark
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Vol.:(0123456789)
Scientometrics
unique method when reporting the number of references. Many studies have followed in the footsteps of de Solla Price, but have only provided the average or median number of references, and thus not interval ratios. All of these studies show a clear tendency: The number of references in scientific publications is growing. About 15 years after the publication of the study by Derek J. de Solla Price, Eugene Garfield noticed a substantial growth in the number of references per item in 37 core biochemical journals (Garfield 1979, 1980). Garfield examined the growth rate by developing an R/S journa
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