THE ‘HALF‐LIFE’ OF PERIODICAL LITERATURE: APPARENT AND REAL OBSOLESCENCE

The expression ‘half‐life’, borrowed from physics, has appeared quite frequently in the literature on documentation since 1960, when an article by Burton and Kebler on The ‘half‐life’ of some scientific and technical literatures was published, although it had certainly been used previously. Burton and Kebler point out that literature becomes obsolescent rather than disintegrating (as in its original meaning), so that ‘half‐life’ means ‘half the active life’, and this is commonly understood as meaning the time during which one‐half of the currently active literature was published. Numerous studies have been carried out, mainly by the analysis of citations, to establish obsolescence rates of the literature of different subjects. Bourne points out that different studies have given widely different results, so that many of the ‘half‐life’ figures reported are not valid beyond the particular sample of literature or users surveyed; certainly they cannot be used as accurate measures for discriminating between different subject‐fields.