The skewness of science in 219 sub-fields and a number of aggregates

Abstract

This paper studies evidence from Thomson Scientific about the citation process of 3.7 million articles published in the period 1998-2002 in 219 Web of Science categories, or sub-fields. Reference and citation distributions have very different characteristics across sub-fields. However, when analyzed with the Characteristic Scores and Scales technique, which is replication and scale invariant, the shape of these distributions over three broad categories of articles appears strikingly similar. Reference distributions are mildly skewed, but citation distributions with a five-year citation window are highly skewed: the mean is twenty points above the median, while 9-10% of all articles in the upper tail account for about 44% of all citations. The aggregation of sub-fields into disciplines and fields according to several aggregation schemes preserve this feature of citation distributions. It should be noted that when we look into subsets of articles within the lower and upper tails of citation distributions the universality partially breaks down. On the other hand, for 140 of the 219 sub-fields the existence of a power law cannot be rejected. However, contrary to what is generally believed, at the sub-field level the scaling parameter is above 3.5 most of the time, and power laws are relatively small: on average, they represent 2% of all articles and account for 13.5% of all citations. The results of the aggregation into disciplines and fields reveal that power law algebra is a subtle phenomenon.

The evaluation of citation distributions

“…The 219 sub-fields include 77 in the Life Sciences, 36 in the Physical Sciences, 73 in Other Natural Sciences, and 33 in the Social Sciences. 4 The main results in Albarrán et al (2011d) can be summarized as follows.…”

“…For our purpose, it would be very convenient to have a hierarchical Map of Science organizing sub-fields, disciplines, and fields in a way agreed upon by the international scientific community. However, extreme doses of scientific inter-disciplinarity have it made impossible to count on such a Map (see Albarrán et al 2011d, for some of the main references in this particularly active research field in Scientometrics). Given the difficulties inherent in any aggregation scheme, to climb up from the sub-field to the discipline and the field levels we use three alternatives routes.…”

“…In the first place, using a large dataset of articles published in more than 8,000 academic or professional journals indexed by Thomson Scientific (TS hereafter), previously known as the Institute for Scientific Information (ISI hereafter), the following two facts are well established Ruiz-Castillo 2011, andAlbarrán et al 2011d).…”

Average-based versus high- and low-impact indicators for the evaluation of scientific distributions

“…1 See inter alia Seglen (1992), Shubert et al (1987) for evidence concerning scientific articles published in the period 1981-85 in 114 sub-fields, Glänzel (2007) for articles published in 1980 in 12 broad fields and 60 middlesized disciplines, Albarrán and Ruiz-Castillo (2009) for articles published in the period 1998-2002 in 22 broad fields, and Albarrán et al (2010a) for these same articles classified in 219 Web of Science categories and three aggregation schemes consisting of a number of disciplines and broad fields.…”

What is a Complex Innovation System?

“…Two papers looked at field level citation distributions for 1998-2002 WoS and Scopus data [43,82]. Albarrán and colleagues used WoS data and Brzezinski used Scopus data.…”