ABSTRACT

The entry discusses the concept of information obsolescence, also referred to as literature decay or aging. Methods used for studying obsolescence, particularly usage data and citation data are discussed. Obsolescence is the general decline over time in the validity or utility of information. The rate of this decline may be uneven and varies according, for instance, to the subject field, type of document, individual journal, or the academic status of the user. Furthermore, a number of factors can explain the decline, and it is not entirely due to the fact that contents have lost their “scientific” value; thus the visibility of the document (the “immediacy effect”) plays its part.