Abstract
This paper has two aims: (i) to introduce a novel method for measuring which part of overall citation inequality can be attributed to differences in citation practices across scientific fields, and (ii) to implement an empirical strategy for making meaningful comparisons between the number of citations received by articles in 22 broad fields. The number of citations received by any article is seen as a function of the article’s scientific influence, and the field to which it belongs. A key assumption is that articles in the same quantile of any field citation distribution have the same degree of citation impact in their respective field. Using a dataset of 4.4 million articles published in 1998–2003 with a five-year citation window, we estimate that differences in citation practices between the 22 fields account for 14% of overall citation inequality. Our empirical strategy is based on the strong similarities found in the behavior of citation distributions. We obtain three main results. Firstly, we estimate a set of average-based indicators, called exchange rates, to express the citations received by any article in a large interval in terms of the citations received in a reference situation. Secondly, using our exchange rates as normalization factors of the raw citation data reduces the effect of differences in citation practices to, approximately, 2% of overall citation inequality in the normalized citation distributions. Thirdly, we provide an empirical explanation of why the usual normalization procedure based on the fields’ mean citation rates is found to be equally successful.
Highlights
The field dependence of reference and citation counts in scientific articles in the periodical literature has been recognized since the beginning of Scientometrics as a field of study
Using a dataset of 4.4 million articles published in 1998–2003 with a five-year citation window and an appropriate citation inequality index, we estimate that the citation inequality attributable to differences in citation practices across the 22 fields represents, approximately, 14% of overall citation inequality
In the dataset used in this paper, how can we interpret the fact that the mean citation in Mathematics is 2.4, about eight and a half times smaller than in Molecular Biology and Genetics where it is equal to 20.4 citations? This paper shows that the striking similarity between citation distributions, causes the citation inequality attributable to different citation practices to be approximately constant over a wide range of quantiles
Summary
The field dependence of reference and citation counts in scientific articles in the periodical literature has been recognized since the beginning of Scientometrics as a field of study (see inter alia [1,2,3]). Given a classification of science into scientific disciplines, this paper develops a measuring framework where it is possible to quantify the importance of differences in citation practices. We use a model in which the number of citations received by an article is a function of two variables: the article’s underlying scientific influence, and the field to which it belongs. In this context, the citation inequality of the distribution consisting of all articles in all fields -the all-fields case- is the result of two forces: differences in scientific influence, and differences in citation practices across fields. The first aim of the paper is how to isolate the citation inequality attributable to the latter, and how to measure its importance relative to overall citation inequality of all sorts
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