Recently a study done by Google Inc. researchers indicates that older papers are increasingly being found and cited by researchers. The November 4, 2014 paper is freely available at arXiv.org and is entitled On the Shoulders of Giants: The Growing Impact of Older Articles. John Bohannon wrote an interesting Science magazine news report about the study that same day. He notes that the Google researchers used Google Scholar data and “analyzed scientific papers published between 1990 and 2013. They divided the papers into nine broad research areas and 261 subject categories. Then they compared the publication dates of the papers cited in all those papers.”
The study authors hypothesize this may be the effective of mass digitization and the increasing cumulative body of born-digital scholarship. In the news report, a commentator offers a different hypothesis, that the growth of the scientific literature is slowing, but offers no evidence for that surprising statement (at least to us librarians who see the growth of open access journals and prices/page counts for subscription journals). A darker hypothesis is that the average quality of papers is decreasing requiring scholars to look further back in time for citable material. However, this last hypothesis is predicated on scholars being particularly diligent in citing only high quality research.