Bornmann, Lutz lutz.bornmann at GV.MPG.DE
Wed Apr 16 09:53:03 EDT 2014

BRICS countries and scientific excellence: A bibliometric analysis of most frequently-cited papers
Lutz Bornmann<>, Caroline Wagner<>, Loet Leydesdorff<>

(Submitted on 14 Apr 2014)

The BRICS countries (Brazil, Russia, India, and China, and South Africa) are noted for their increasing participation in science and technology. The governments of these countries have been boosting their investments in research and development to become part of the group of nations doing research at a world-class level. This study investigates the development of the BRICS countries in the domain of top-cited papers (top 10% and 1% most frequently cited papers) between 1990 and 2010. To assess the extent to which these countries have become important players on the top level, we compare the BRICS countries with the top-performing countries worldwide. As the analyses of the (annual) growth rates show, with the exception of Russia, the BRICS countries have increased their output in terms of most frequently-cited papers at a higher rate than the top-cited countries worldwide. In a further step of analysis for this study, we generate co-authorship networks among authors of highly cited papers for four time points to view changes in BRICS participation (1995, 2000, 2005, and 2010). Here, the results show that all BRICS countries succeeded in becoming part of this network, whereby the Chinese collaboration activities focus on the USA.

Available at:

The substantive and practical significance of citation impact differences between institutions: Guidelines for the analysis of percentiles using effect sizes and confidence intervals
Richard Williams<>, Lutz Bornmann<>

(Submitted on 12 Apr 2014)

In our chapter we address the statistical analysis of percentiles: How should the citation impact of institutions be compared? In educational and psychological testing, percentiles are already used widely as a standard to evaluate an individual's test scores - intelligence tests for example - by comparing them with the percentiles of a calibrated sample. Percentiles, or percentile rank classes, are also a very suitable method for bibliometrics to normalize citations of publications in terms of the subject category and the publication year and, unlike the mean-based indicators (the relative citation rates), percentiles are scarcely affected by skewed distributions of citations. The percentile of a certain publication provides information about the citation impact this publication has achieved in comparison to other similar publications in the same subject category and publication year. Analyses of percentiles, however, have not always been presented in the most effective and meaningful way. New APA guidelines (American Psychological Association, 2010) suggest a lesser emphasis on significance tests and a greater emphasis on the substantive and practical significance of findings. Drawing on work by Cumming (2012) we show how examinations of effect sizes (e.g. Cohen's d statistic) and confidence intervals can lead to a clear understanding of citation impact differences.

Available at:


Dr. Dr. habil. Lutz Bornmann
Division for Science and Innovation Studies
Administrative Headquarters of the Max Planck Society
Hofgartenstr. 8
80539 Munich
Tel.: +49 89 2108 1265
Mobil: +49 170 9183667
Email: bornmann at<mailto:bornmann at>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the SIGMETRICS mailing list