A Reproducible Journal Classification and Global Map of Science Based on Aggregated Journal-Journal Citation Relations

A number of journal classification systems have been developed in bibliometrics since the launch of the Citation Indices by the Institute of Scientific Information (ISI) in the 1960s. The best known system is the so-called “Web-of-Science Subject Categories” (WCs). Each system has its own advantages and disadvantages. Using the Journal Citation Reports 2014 of the Science Citation Index and the Social Science Citation Index (n of journals = 11,149), we examine the options for developing an unambiguous classification of the journals into subject categories on the basis of aggregated journal-journal citation data. Combining routines in VOSviewer and Pajek, a tree-like classification is developed which can be reproduced unambiguously. At each level one can generate a map of science for all the journals subsumed under the category. Nine major fields are distinguished at the top level, with the social sciences as a single field (n of journals = 3,131). In this study, further decomposition of the social sciences is pursued for the sake of example with a focus on journals in information science (LIS) and science studies (STS). The classification improves alternative options by removing subjective judgement and avoiding the problem of randomness in the seed number that has made algorithmic solutions hitherto irreproducible. A non-subjective map and classification can provide a baseline for measuring the effectiveness of policy interventions. Maps can be compared between years, and change in the (social) sciences can be indicated.