Multiplicative and fractional strategies when journals are assigned to several subfields

Journal of Informetrics

Costas

2014

Self Cite

This paper exploits a unique 2003-2011 large dataset, indexed by Thomson & Reuters, consisting of 17.2 million disambiguated authors classified into 30 broad scientific fields, as well as the 48.2 million articles resulting from a multiplying strategy in which any article co-authored by two or more persons is wholly assigned as many times as necessary to each of them. The dataset is characterized by a large proportion of authors who have their oeuvre in several fields. We measure individual productivity in two ways that are uncorrelated: as the number of articles per person, and as the mean citation per article per person in the 2003-2011 period. We analyze the shape of the two types of individual productivity distributions in each field using size-and scale-independent indicators. For productivity inequality, we use the coefficient of variation. To assess the skewness of productivity distributions we use a robust index of skeweness, as well as the Characteristic Scores and Scales approach. For productivity inequality, we use the coefficient of variation. In each field, we study two samples: the entire population, and what we call "successful authors", namely, the subset of scientists whose productivity is above their field average. The main result is that, in spite of wide differences in production and citation practices across fields, the shape of field productivity distributions are very similar across fields. The parallelism of the results for the population as a whole and for the subset of successful authors when productivity is measured as mean citation per article per person, reveals the fractal nature of the skewness of scientific productivity in this case. These results are essentially maintained when any article co-authored by two or more persons is fractionally assigned to each of them.Acknowledgements. This is the third version of a Working Paper in this series with the same title whose second version appeared in May 2014. This paper was conceived while Ruiz-Castillo enjoyed the hospitality of the Centre for Science and Technology Studies, Leiden University, The Netherlands, during the 2013 spring term. Ruiz-Castillo also acknowledges financial help from the Spanish MEC through grant ECO2010-19596. The authors acknowledge fruitful conversations with Raquel Carrasco, as well as comments from the participants in a CWTS seminar. All remaining shortcomings are the sole responsibility of the authors.

Section: Comparison Of Results With the Previous Literaturesupporting

confidence: 73%

The skewness of scientific productivity

Journal of Informetrics

Costas

2014

Self Cite

“…However, gap differences are not very large: only in 20 cases, of which 17 reflect a worsening of the EU situation, this difference in absolute value is 10 % greater than the US/EU gap under the multiplicative strategy. As in Herranz and Ruiz Castillo (2012a), the similarity of citation characteristics of articles published in journals assigned to one or several sub fields guarantees that choosing one of the two strategies may not lead to a radically different picture in this practical application. Secondly, after raising the Critical Citation Line from the 80th to the 95th percentile of world citation distributions the EU is ahead of the US in exactly the same number of sub fields as before, namely, 30.…”

Section: Discussionmentioning

confidence: 99%

“…In this way, the space of articles is expanded as much as necessary beyond the geographical extended count in what we call the double extended sub field count, which in our case reaches 6,512,031 articles or 57.7 % more than the number of articles in the geographical extended count. However, this is not that worrisome in the sense that, since this strategy does not create any interdependencies among the sub fields involved, it is still possible to sepa rately investigate every sub field in isolation, independently of what takes place in any other sub field (see Herranz and Ruiz Castillo (2012a) for a comparison of the two strategies).…”

Section: Assignment Of Articles To Geographical Areas and To Sub Fieldsmentioning

confidence: 99%

The end of the “European Paradox”

Herranz

2012

Scientometrics

Self Cite

This paper evaluates the European Paradox according to which Europe plays a leading world role in terms of scientific excellence, measured in terms of the number of publications, but lacks the entrepreneurial capacity of the US to transform this excellent performance into innovation, growth, and jobs. Citation distributions for the US, the European Union (EU), and the Rest of the World are evaluated using a pair of high and low impact indicators, as well as the mean citation rate (MCR). The dataset consists of 3.6 million articles published in 1998 2002 with a common 5 year citation window. The analysis is carried at a low aggregation level, namely, the 219 sub fields identified with the Web of Science categories distinguished by Thomson Scientific. The problems posed by international co authorship and the multiple assignments of articles to sub fields are solved following a multiplicative strategy.

“…As in Herranz and Ruiz-Castillo (2011a), it can be shown that the number of articles and citations in the …”

Section: The Multiplicative Strategy In the Geographical Extenmentioning

confidence: 92%

“…As advocated in Herranz and Ruiz-Castillo (2011a), there are two reasons why the multiplicative strategy might be preferable to deal with this problem.…”

Section: Reasons For the Multiplicative Strategymentioning

confidence: 99%

Sub-field normalization in the multiplicative case: High- and low-impact citation indicators

Herranz

2012

Research Evaluation

This paper uses high-and low-impact citation indicators for the evaluation of the citation performance of research units at different aggregate levels. To solve the problem of the assignment of individual articles to multiple sub-fields, it follows a multiplicative strategy according to which each paper is wholly counted as many times as necessary in the several categories to which it is assigned at each aggregation level. To control for wide differences in citation practices at the lowest level of aggregation, we apply a novel sub-field normalization procedure in the multiplicative case. The methodology is applied to a partition of the world into three geographical areas: the U.S., the European Union (EU), and the Rest of the World. The main findings are the following two. (i) Although normalization does not systematically bias the results against any area, it reduces the U.S./EU highimpact gap in the all-sciences case by a non-negligible 14.4%. (ii) The dominance of the U.S. over the EU in the basic and applied research published in the periodical literature is almost universal at all aggregation levels. From the high-impact perspective, for example, the U.S. is ahead of the EU in 77 out of 80 disciplines, and all of 20 fields. For all sciences as a whole, the U.S. high-impact indicator is 61% greater than that of the EU.