The CiteScore journal impact metric measures the average citations received in a four-year time window to selected documents published in the same four years. The 2019 CiteScore is based on citations received in 2016-2019 to articles, reviews, conference papers, book chapters, and data papers published in 2016-2019, and divides this by the number of these documents published in 2016-2019. CiteScore covers all journal titles in Elsevier's Scopus database and is released once a year.