In-Depth Examination of Coverage Duration: Analyzing Years Covered and Skipped in Journal Indexing

Journals that have consistently maintained uninterrupted indexing over an extended period can be assumed to possess stability and sustainability in journal indexing. Building on this assumption, the objective of this study is to scrutinize the years omitted in the indexing of Scopus-indexed journals. To conduct this study, three coverage duration indicators—nyears-covered (total years covered), nyears-skipped (years skipped), and skipped/covered ratio (proportion of years skipped to total years covered)—were formulated. Data from SCImago Journal Rank (SJR) for 2022, consisting of 16,762 records (62% of downloaded data) with a coverage duration of 25 years or less, were used for this study. The results revealed that around 10% of Scopus-indexed journals experienced exclusions or coverage gaps. Longer coverage correlates positively with documents published, h-index, and citations, while skipped years decrease with these indicators. Open access (OA) journals exhibited a lower skipped/covered ratio than non-OA journals, suggesting a better sustainability of indexing than non-OA journals. Disciplinary differences in Scopus journal coverage duration revealed notable variation, suggesting that coverage duration indicators can be effectively used to evaluate journal stability within Scopus. Overall, the coverage gaps reflect Scopus’s efforts to regulate the journals it indexes. The coverage duration indicators proposed in this study can be applied to assess the stability of periodicals in any database, providing insights into the broader dynamics and quality standards maintained by a database, where the database periodically adds and removes its indexed contents.