Letter to the Editor—A Comment on the Morse-Elston Model of Probabilistic Obsolescence

Morse and Elston have constructed a probabilistic model of obsolescence and fitted it to the circulation of books in a library. This note presents a modification of their model and fits it to their results to account for time dependence of their original parameter α. This revised model can be used to describe the phenomena of obsolescence as seen in such a case as the usage over time of books concerned with scientific subjects.