Does open access to published articles lead to increased citations?
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Open Access and Increased Citations: A Comprehensive Analysis
Introduction to Open Access Citation Advantage
The concept of Open Access Citation Advantage (OACA) suggests that articles made freely available to the public are cited more frequently than those behind paywalls. This hypothesis has been a subject of extensive research and debate over the past two decades. Various studies have attempted to quantify the impact of open access (OA) on citation rates, yielding mixed results.
Systematic Reviews and Meta-Analyses
A systematic review encompassing 134 studies found that 47.8% confirmed the existence of OACA, while 27.6% did not find any advantage, and 23.9% observed OACA only in subsets of their samples. This indicates a significant interest in the topic, although the heterogeneity and quality of the studies pose challenges for generalization.
Longitudinal and Comparative Studies
A longitudinal bibliometric analysis of articles published in the Proceedings of the National Academy of Sciences (PNAS) revealed that OA articles were cited more frequently than non-OA articles. Specifically, OA articles were twice as likely to be cited within the first 4-10 months after publication, with the odds ratio increasing to 2.9 after 10-16 months. This study underscores the immediate recognition and citation benefits of OA publishing.
Field-Specific Insights
In the field of radiology, a study found that OA articles were significantly more frequently cited, downloaded, and shared compared to subscription-based articles. Similarly, research in ecology journals demonstrated that OA articles received more citations than non-OA articles, with the citation advantage being consistent across various countries and independent of the economic status of the citing scientists.
Impact Factor and Citation Correlation
Interestingly, the impact factor (IF) of a journal does not significantly influence the citation rates of articles published in OA journals. A study comparing OA and non-OA journals found that while non-OA journals showed a moderate correlation between IF and citations, this was not the case for OA journals. This suggests that the accessibility of OA articles may play a more crucial role in citation rates than the prestige of the journal.
Declining Open Access Advantage
An analysis of biological and medical journals employing author-choice OA models reported a small but significant increase in citations for OA articles. However, the OA advantage appeared to be declining over time, from 32% in 2004 to 11% in 2007. This trend indicates that while OA may initially boost citations, its long-term impact may diminish.
Contradictory Findings
Not all studies support the OACA hypothesis. For instance, a randomized controlled trial found no significant citation advantage for OA articles, although these articles did receive more downloads. Another study using Web of Science metadata concluded that OA articles experienced a citation advantage in very few subject areas, and the advantage was often limited to whether the article was cited at all.
Conclusion
The relationship between open access and increased citations is complex and varies across disciplines and study designs. While many studies confirm the existence of an OACA, others find no significant advantage or report a declining trend over time. The accessibility and visibility provided by OA publishing undoubtedly play a role in enhancing citation rates, but other factors such as journal impact factor and field-specific dynamics also contribute. Further research is needed to fully understand the long-term implications of OA on citation metrics.
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