Revisiting 'obsolescence' and journal article 'decay' through usage data: an analysis of digital journal use by year of publication

The publication age or date of documents used (or not used) has long fascinated researchers and practitioners alike. Much of this fascination can be attributed to the weeding opportunities the data is thought to provide for libraries in their never-ending battle to find the space to accommodate their expanding collections. In general journal article age studies have shown an initial increase in use/citation, then a gradual or sharp decline, depending on the discipline concerned. This characteristic has been termed obsolescence or decay and was largely measured, in the absence of accurate journal usage/borrowing data, by citations. In the sciences the decay rate was shown to be the greatest. This was largely put down to the rapid obsolescence of much scientific content. New research findings, methods or ensuing events rendered the material obsolescent. Of course, when reviewing the data we need to be reminded of the fact that citation studies reveal ‘‘use’’ by authors, whereas library loans or downloads represent actual use by readers, and it is readers that libraries and digital libraries principally target. Clearly the fall of in use with time must have also been a function of the way that libraries arranged their material (in reverse chronological order); a lack of time and patience will inevitably result in readers aborting their searches after a few years and those few years will be the most recent ones. Similarly, it must also have been a function of the difficulties of searching hard-copy back volumes/issues in libraries over time.