What is the effect of country-specific characteristics on the research performance of scientific institutions? Using multi-level statistical models to rank and map universities and research-focused institutions worldwide

Bornmann, Stefaner, de Moya Anegón, and Mutz (in press) have introduced a web application (www.excellencemapping.net) which is linked to both academic ranking lists published hitherto (e.g. the Academic Ranking of World Universities) as well as spatial visualization approaches. The web application visualizes institutional performance within specific subject areas as ranking lists and on custom tile-based maps. The new, substantially enhanced version of the web application and the multilevel logistic regression on which it is based are described in this paper. Scopus data were used which have been collected for the SCImago Institutions Ranking. Only those universities and research-focused institutions are considered that have published at least 500 articles, reviews and conference papers in the period 2006 to 2010 in a certain Scopus subject area. In the enhanced version, the effect of single covariates (such as the per capita GDP of a country in which an institution is located) on two performance metrics (best paper rate and best journal rate) is examined and visualized. A covariate-adjusted ranking and mapping of the institutions is produced in which the single covariates are held constant. The results on the performance of institutions can then be interpreted as if the institutions all had the same value (reference point) for the covariate in question. For example, those institutions can be identified worldwide showing a very good performance despite a bad financial situation in the corresponding country. 1 Introduction International rankings have been published for around 10 years: in 2003, the Shanghai Jiao Tong University published the Academic Ranking of World Universities (ARWU) with The Times Higher Education QS Top University Ranking (THE QS) following a year later in 2004. " Despite significant volumes of criticism and commentary, and some boycotts by HEIs [Higher Education Institutions], rankings have become an increasingly popular way to compare higher education performance and productivity " (Hazelkorn, 2013, p. 9). In a list of the most prominent rankings Hazelkorn (2013) names 11 different international rankings (see also Rauhvargers, 2011). The most important source of data used for the various rankings are abstract and citation databases of peer-reviewed literature (primarily Scopus, which is provided by Elsevier and the Web of Science, WOS, from Thomson Reuters). Publication and