Tracking content updates in Scopus (2011-2018): a quantitative analysis of journals per subject category and subject categories per journal

International audienceThe aim of this study is to track Scopus content updates since 2011 and more particularly the distribution of journals into subject areas. An unprecedented corpus of data related to sources indexed in Scopus has been created and analyzed. Data shows important fluctuations regarding the number of journals per category and the number of categories assigned to journals. Those variations are very irregular, invisible to the average user and unpredictable over time. They question the reliability of studies based on Scopus data if no precautions are taken. The suggestion is made that category changes should not systematically be applied to all previously indexed publications of a journal, but only to those that will be indexed in Scopus after the new assignment is made