An analysis of factors contributing to PubMed's growth

We studied the factors (recent and older journals, publication types, electronic or print form, open or subscription access, funding, affiliation, language and home country of publisher) that contributed to the growth of literature in Biomedical and Life Sciences as reflected in PubMed in the period 2004-2013. Only records indexed as journal articles were studied. 7364,633 journal articles were added in PubMed between 2004 and 2013 (48.9% increase from 2003). Recently launched journals showed the greater increase in published articles, but older journals contributed the greater number of articles. The observed growth was mainly attributed to articles to which no other PubMed publication type was assigned. Articles available in both print and electronic form increased substantially (61.1%). Both open (80.8%) and subscription access (54.7%) articles increased significantly. Funding from non-US government sources also contributed significantly (74.5%). Asian (114%) and European (34.9%) first author affiliation increased at a higher rate than American publications (7.9%). English remained the predominant language of publications. USA- and England-based organizations published a gradually increasing body of literature. Open access, non-US government funding and Asian origin of the first author were the factors contributing to literature growth as depicted in PubMed. A better assignment of publication types is required.