Publication: The skewness of science in 219 sub-fields and a number of aggregates
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2010-10
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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 size and
scale independent, the shape of these distributions appear extraordinarily 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. 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.