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1Crespo, J.A. ; Herranz, N. ; Li, Y. ; Ruiz-Castillo, J.: ¬The effect on citation inequality of differences in citation practices at the web of science subject category level.
In: Journal of the Association for Information Science and Technology. 65(2014) no.6, S.1244-1256.
Abstract: This article studies the impact of differences in citation practices at the subfield, or Web of Science subject category level, using the model introduced in Crespo, Li, and Ruiz-Castillo (2013a), according to which the number of citations received by an article depends on its underlying scientific influence and the field to which it belongs. We use the same Thomson Reuters data set of about 4.4 million articles used in Crespo et al. (2013a) to analyze 22 broad fields. The main results are the following: First, when the classification system goes from 22 fields to 219 subfields the effect on citation inequality of differences in citation practices increases from ?14% at the field level to 18% at the subfield level. Second, we estimate a set of exchange rates (ERs) over a wide [660, 978] citation quantile interval to express the citation counts of articles into the equivalent counts in the all-sciences case. In the fractional case, for example, we find that in 187 of 219 subfields the ERs are reliable in the sense that the coefficient of variation is smaller than or equal to 0.10. Third, in the fractional case the normalization of the raw data using the ERs (or subfield mean citations) as normalization factors reduces the importance of the differences in citation practices from 18% to 3.8% (3.4%) of overall citation inequality. Fourth, the results in the fractional case are essentially replicated when we adopt a multiplicative approach.
Objekt: Web of Science
2Herranz, N. ; Ruiz-Castillo, J.: Multiplicative and fractional strategies when journals are assigned to several subfields.
In: Journal of the American Society for Information Science and Technology. 63(2012) no.11, S.2195-2205.
Abstract: In many data sets, articles are classified into subfields through the journals in which they have been published. The problem is that while many journals are assigned to a single subfield, many others are assigned to several. This article discusses a multiplicative and a fractional strategy to deal with this situation. The empirical part studies different aspects of citation distributions under the two strategies, namely: the number of articles, the mean citation rate, the broad shape of the distribution, their characterization in terms of size- and scale-invariant indicators of high and low impact, and the presence of extreme distributions, that is, distributions that behave very differently from the rest. We found that, despite large differences in the number of articles according to both strategies, the similarity of the citation characteristics of articles published in journals assigned to one or several subfields guarantees that choosing one of the two strategies may not lead to a radically different picture in practical applications. Nevertheless, the characterization of citation excellence through a high-impact indicator may considerably differ depending on that choice.