THE AGING OF SCIENTIFIC LITERATURE: A CITATION ANALYSIS

Scientific writings age; individual documents, issues or volumes of scientific journals are, eventually, less valued and less used with the passage of time. Long periods of time, say more than several decades, render portions of the literature obsolete, and ‘aging’ is evident. However, controversy has developed recently about quantitative models, particularly Brookes, which proposes a systematic exponential aging process for the corpus of library periodical holdings. In disagreement with these models, Sandison presents use patterns showing no aging; and Line points to methodological difficulties in demonstrating aging. Both the models, and the questions raised regarding their validity are of considerable interest and importance to our understanding of the nature of scientific information and the management of collections. We show, here, that citation data conform well to the Brookes model, but the chief findings regard the nature of the aging process and its apparent range within scientific literatures. A scientific journal which is used as an archive ages slowly; one which supports a research front ages quickly. Aging depends not merely on the material itself, but its user, and a single journal may be aged very differently by different user communities. Lastly, aging rates vary among journals, and it is relatively easy to identify journals which age at about the rate at which the literature grows and journals which appear to exhaust most of their utility within a few years.